Don't be sorry those are great questions!
I'll address each one specifically:
Now I'm thinking about what to do when the calendar turns 75 days out. I read the advice about getting online at midnight to start booking things -- that is if anything is left by then. Sounds like Palo is the hot ticket and I am very confused about how the rotations work and what we might miss on board if we go there for dinner. Since it is our first cruise and we have little ones who love to be entertained by all things Disney, should I just avoid Palo so we don't miss anything going on while we are at dinner? We have main dining.
That is the challenging thing. Its hard to get a feel for things until you have been on a cruise and actually done it and know what to miss and what not to miss. LOL our first cruise Palo ended up on Pirate night.. (and we actually liked that!) But there are a lot of variables to take into consideraton.
First off as far as Palo goes High Tea are the most coveted reservations. This is because it is a very limited seating. I have never been to a High Tea, so I can't tell you too much about it. There was one reservation left at 90 days out on our last cruise (at midnight on day 90) and it went immediately so you would probably not be able secure these reservations.
Brunch is the next most difficult Palo reservation to get. On my last cruise there were 3 (three) brunch reservations available at midnight on day 90. They went immediately (we got one of them). Some of our dis meet group were successful in getting brunch reservations once onboard but some were not.
Dinner had a lot of options. At midnight on day 90 there were many different time slots for each night of the cruise still available. We were easily able to select what we wanted. By day 75 there were still plenty of options for dinner open and I do believe everybody who wanted a dinner eventually got one, although many did not get the day or times they desired. We also had an itinerary change and a rotaiton change so most of our group were at Rockin Bar d changing our rotations or Palo or both. Most were able to do this.
So that give you a little bit of an idea of what to expect come 75 days out. As far as how to make your choices, that will take a little research. I can tell you that you probably will not want to miss your "show" night at Animator's Palate, which will (sigh,
should-they do change things up sometimes) be either night 1,2, or 4 depending on your rotation. There is a very special surprise that your kids will enjoy. You can check out the "rotational" menus and see if there is one you like less than the rest (we don't care much for Parrot Cay's rotational menu for example). You won't miss anything special in PC or Lumiere's on the rotation nights. Villains night I have not experienced yet. Pirate night there is a fun parade in the Dining Room, the servers are in Pirate costumes and a special Pirate menu. So you might not want to miss that night (night 5). Nights 6 and 7 have special menus (Captain's Gala and Til We Meet Again) but nothing too much of events in the dining room. There is a big final parade of servers on the last night. So you have to weigh those things and try to narrow it down to a night you think you might want to go, then call
DCL or your TA and request the dining rotation that will put you in the restaurant you want to be in that night. For instance we like to go to Palo on night 2. So we request the rotation that puts us in PC on night 2 and make our Palo for that night. Being a newbie I would see what is available for Palo at 75 THEN make your rotation request around it. Sometimes if you want Palo you kindof have to take what you can get and then schedule around it.
I heard that you get the Tea Party tickets on board so I can't book that online. So what else is there to book on day 75 besides spa stuff? I'm not in need of any excursions as my family is doing the hop on hop off thing in KW, Captain Marvin's with Judy's group in GC and Nachi in Cozumel. The only thing we haven't planned for is CC and I'm thinking that my girls will love the kids beach and when they get tired of that we'll do the family beach. So what have I forgotten?
Not much, except CC reservations like floats and snorkel gear, etc. which you can do on the island. The kids beach and family beach on CC are one and the same. Unless you meant in the kids club (Scuttle's) that isn't actually a beach, it is located "inland" (yes there is a sand pit but it is not on the water).
We are doing all the same excursions as you!!
Looking forward to it!
Of ocurse you aren't in need of Flounder's Reef reservations but the inital 20 hours are also available for booking for those of us who meet that criteria.
And a logistics question about the online booking : say I'm online at midnight and still confused when I see what choices are out there. Does the online system kick me out if I don't make a decision within a set period of time (say five minutes or what)?
Yes, you do get logged off for inactivity, I think it is 10 minutes.
Do slots for Palo start to disappear before my eyes while I'm making a decision?
Yes they do, I saw the High Tea disappear before my very eyes. LOL. They don't pop away until you refresh or try to book though, then you just get an error and go back to the now-open choices (they have changed the site up a bit since the last time I did this so I am not 100% sure it still works like that, but it did back last time I used it)
Can I book something that night and then get online another day with changes or additions?
Sure can, we changed our Flounders up many times.
Hope that helps, and I didn't confuse you. I know that is a lot of info!
! Apologies if I have, and can they please join?!!
The heat and humidity in South Jersey has been horrible and right now - the Air Conditioner at work is broken!
At least now you have a diagnosis and can treat accordingly. I developed asthma in my teens and once I had it under control, it hasn't caused too many issues for me. I really hope you start to feel better very soon 
