If this is a first visit, then you won't need or miss hopping. I'm not trying to harp on this part - but it's not really tiring to hop between parks. It's actually the opposite; a chance to take a break.
In the warm months, I'll suggest that you likely will want some kind of afternoon break. Again, I'm not saying it has to be, or should even be hopping. There are lots of ways to get a little quiet time in the air conditioning. A simple one is visiting the nearest deluxe resort. You can often take a boat or monorail to get there (young kids willl see it as another 'ride'), then sit in a comfy lobby, grab a cool drink/lunch, tour the fun stuff, maybe even listen to some relaxing music. It's also a good way to dodge the afternoon thunderstorm!
If the four year old is willing to ride ina stroller, you may want to bring a compact one.
You also probablywant to think about dining. If you are staying offsite, then you are free to eat some meals offsite. My suggestion woudl be thinking up some combination. I'd suggest quick breakfasts - at your condo most days - lunch onsite - and maybe dinner offsite. If youare staying very clsoe to WDW- then you could maybe do late lunches offsite- followed by onsite dinners. But picking between the two - offsite dinners will likely equal the lower price point. Also, if you plan on eating (most) dinners offsite then you can avoid the 180day reservations craziness. I'm sure some offsite places will require erservations, but not 180 days out.
There'a great DIS thread on 'best offsite dining' with lots of suggestions. It is an old thead though - so do look towards the more recent posts.
For me, thinking about my strategy, it really helps to know where I'm going to be staying. So I'd encourage you get that squared away quickly.
One place you might want to look into is Shades of Green.
You talked about renting a car, soI assume you are thinking about flying; I'd start your airfare search now. In some cases you might be best off booking now, sometimes better off waiting for a bit.
Now's also a good time to start the rental car search - but probably you'll find better deals as dates get closer.
Also, this may be obvious - establish your baseline budget. It sort of sounds like you have done that - but Tickets and transportation are sort of fixed costs. Food is a much more variable cost. Make sure everyone in your group is on the same page when it comes to your overall budget plans.
You'll need to coordinate your arrival times. It might make sense for everyone to use one rental car; it might also make sense for one subgroup to use a towncar service (one way?) or taxi. It depends where you are staying. You may be near the airport, you may be over an hour away.
You should familiarize yourself with the basic layout of WDW, and come up with some sort of rough plan of rides you want to see. I would not create any hard plan of what order and time - but maybe a list of rides thata re top priorities. read about fastpass, know how it works. It's free, and will save you from waiting in long lines. (but only certain rides)
If you have a smartphone with GPS - that will come in handy. If you have a non-phone GPS that would also come in handy.
IF you are eating in your condo, then you'll want to map out the nearest grocery store. Personally I like Publix. There's also an amazing Whole Foods near Sand Lake Rd/I-4. It's an expensive place to shop - but the food quality is very high. As WF's go, that one is new, and really nice. Like they have in-store brick pizza oven, and fresh sqeezed orange juice. It won't feel like 'eating in.' Publix is a little more mainstream kind of grocery store, but they also have lots of fresh prepared foods. Not the junky kind of prepared foods - high quality. Some Publix have more offerings. I think both also sell beer and wine - at least the ones I've visited.
There are also several Walmarts and Targets around. When We've tried
Walmart, I found that they tend to sell mostly very large boxes of items, so it didn't end up saving us money. We weren't going to eat the mega box of Cheerios, for example. But we did eat EVERY bite of the fresh cornbread we got at Whole Foods, and we've done well going to Publix. Another chain you'll find all over the area are 24hour Walgreens. If you just want suncreeen shampoo, and a FEW limited grocery items (the kind of stuff TSA limits these days), it's okay. One advantage of Walmart is they have LOTS of Disney stuff. It's like an in-house
Disney store. I'm not going to knock the quality either. The last time we went, they had some cute items for quite a bit lower than WDW prices. We went tothe Walmart near route 192. i've never tried Targets in the area, but there are several.
