Hi! We are also an Australian family, kiddos are 11 & 12 (both girls), we have been a few times so some of our dining will be repeats, and some new to us. We will be there over Christmas so I have made a few more TS bookings than usual so we don't miss out on a seat somewhere when we want out of the crowds. It's our second time going at Christmas too, though the last time was five years ago. My thinking this year with my planning has been... can I get this experience (or something similar enough to it) at home - or can I get it in the parks without it being a dining experience?
We have a longer stay so more ADRs, but I'll let you know what we're looking at doing and why so you can decide what's more important to you (ie, are you after better meals, or atmosphere/theming, the ability to enter a park early, or characters... )
Magic Kingdom -
Skipper Canteen: this is new to us, but the menu looks like it will work for our family and the Skipper humour is fun

BOG (Be Our Guest): We have done this before and while I wasn't actually totally wowed by it, this time we have a pre-park opening booking which means being able to wander through parts of the park before the crowds descend. We've done this with Crystal Palace in the past and it has always been special. These days Crystal Palace isn't a particularly useful PPO booking because the park is open up through mainstreet for everyone before opening now, which means walking to the restaurant is not the quiet, special (magical!) experience it once was. (Crystal Palace is still a fun place to get a meal though if you're into Winnie the Pooh, Tigger, Eeyore etc...). Back to BOG though - it's a restaurant you can book for, and you can even make your order ahead of time online, but you don't need to tip here as it's officially a Quick Service location.
This time around we are not doing Cinderella's Royal Table because we have done it before and while it was fun to dine in the castle, the girls are no longer into princesses and it's not a 'wow' meal for the price. You can also do this though as a pre-park opening meal which might add to its value for your family.
Hollywood Studios -
Sci-Fi Dine In Theatre: My kids have great memories of this and are super keen to do it again! The meals are generally burgers & fries fare, but I'm a fusspot lol and found something I enjoyed. Great fun to do at least once. (We have also done the 50s prime time before and while I remember it being good, I don't remember it as fondly as sci-fi and nor do the kids).
This year we are also doing Hollywood & Vine/Minnie's Seasonal/Fantasmic! package - not because we expect it to be amazing, but because it is something we haven't done, and the kids are likely to enjoy it. I probably wouldn't choose it first.
I've also booked Mama Melrose's this year, but haven't done that before.
Epcot:
This year we are doing Chefs de France (new to us), San Angel Inn (I have zero memories of the food lol, but LOVED the atmosphere! Not like anything we get in Australia), Tokyo Dining (this *is* like something we can get in Australia but we enjoy sushi - I wouldn't pick it first), Coral Reef (I remember a great big turtle hovering right beside us the last time we ate here! However - everything you see in this restaurant [in terms of the aquarium] you can see from outside the restaurant too, so you can still enjoy that aspect without eating here), and Garden Grill - rotating restaurant with Chip and Dale. We are doing this as a pre park opening too, with the hopes that we will be right there to jump on Soarin' (which can get long lines) when we are done!

. We have done Via Napoli and I literally have almost zero memories of it lol. Epcot also has some good quick service places too though, so if you wanted to save some $$ you could still choose to eat Japanese/Chinese/Mexican/French etc etc, and still experience the atmosphere wandering around inside each of the countries. The big food court over by Garden Grill is also good with lots of healthy as well as delicious options. Hmm I'm not sure I've helped here but the point of my ramblings is that you can eat well here by eating Quick Service, and still experience everything Epcot has to offer. Love Epcot
Animal Kingdom:
We haven't done Rivers of Light before and so have decided to do a ROL package at Tusker House. We have done breakfast at Tusker House before and the kids enjoyed that... we could choose from Tiffins or Tusker for the ROL package and while the food at Tiffins is more up my alley, ultimately I decided that for the money, I can eat at places in Australia that have meals comparible to Tiffins, but I can't recreate Tusker. So Tusker it is

I have booked Yak & Yeti too as I remember the biggest, most amazing Tuna Salad here, though I don't recall anything terribly memorable about the restaurant itself. If we decide to cancel this booking later, it won't be a massive loss. Except for where that salad is concerned ha ha.
Everywhere else:
We have eaten at California Grill twice - once was great, once was so-so, but both times the view of the fireworks from up here was pretty special and so we have booked to do it again. I tend to book it on a Christmas or Halloween party night if dates are right so we can see the fireworks we won't see since I don't tend to spend the extra going to parties (kids used to be too young, and now that they are older I know they'd much prefer the Halloween party to the Christmas Party. They are all about trick or treating... ie the lollies).
Dessert Party - We have done this twice, it's a nice view of the fireworks but at this year's prices I know it's not worth it for us. We have other plans for fireworks views. However for the times we have done it, it has been memorable and worthwhile. Kids would both like to do it again but I can't make it work with my plans anyway lol.
'Ohana: we have eaten here twice, once at a table that had a view of the fireworks at the right time (awesome experience!) and once not (but we were able to get up and see them if I recall). I remember it being crazy busy last time but for some reason, am looking forward to doing it again lol.
T-Rex and Rainforest Cafe: these are so unlike anything we can do in Australia and my kids are dying to do both again. Check out videos and see what you think. If I had to pick just one, I'd go for Rainforest. Fun shop to check out before and after too. If going to T-Rex, request not to be in the ice-room - full of bright changing colours, I found that super hard on my eyes!
V&A: We did Victoria & Albert's one year - very special, but we did it sans kids. Tossing up whether to do it again but not convinced (I see the menu doesn't actually change *that* much year to year and we'd have to take kids this time and I don't know that they'd appreciate it like I would. Don't even know the hubby would appreciate it like I would lol!)
I have booked something at the Grand Floridian Cafe this year, but that is mostly to make sure we have a reason to visit the GF and check out the holiday decorations. (We have eaten there before and it was good, but not super different to a meal we could get in Aus). Actually, thinking about it, I've booked a 1900 Park Fare breakfast there this year too, as I try and work out what we should do for Christmas Day.
The boathouse: enjoyed this, but not totally different to something we'd get in Australia - except for those Aquacars! Def. tempted to do those this time. But you don't eat in those lol.
Earl of Sandwich is something easy & yum do as QS during the holiday period - Turkey & cranberry sandwiches etc. A few years back we signed up to their loyalty progam and all ate free
In terms of your planning - you are coming a long way, so if I were you I would make any reservations you think you might want, then research them to death (everyone over-researches, right??). It *is* possible to pick up desirable ADRs after the 180-day mark (particularly around the 45-day mark, when people cancel trips) but if you are visiting in a busy time, it's less stressful to have a reservation or two you might cancel later, than be trying to chase a reservation you didn't initially make kwim.