If there is a way to leave the 2 year old in the hotel room with a spouse or relative, that would make things easier. I don't see how people can enjoy the park pushing a stroller, and the 2 year old won't remember any of it.
I guess they should just leave the 2 yr in the room for the entire trip since they won't remember WDW either.
There is plenty that the 2 yr old will enjoy and remember too. Both parks have plenty that the kids can do, but IOA probably has more that the older 2 will want to do.
Give me an idea of what they enjoy at WDW to help you a little more. Here are a few things at each park that all your kids can do
US... (all of these my DD did at 3)
ET
Animal Plant live show
Earthquake
Wlid West stunt show
Fivel's Playland
A Day in the park with Barney (play area and a show)
Woodywoodpeckers Kids zone
Twister
Jaws (DD didn't like it but loved the now gone Kongfrontation which was scarier)
The older 2 could also do
Back to the Future
Men in Black
Terminator 3 D
IOA for all 3
One fish 2 fish
Caro Seuss el
If I ran the zoo
Cat in the Hat
Camp Jurassic
Me ship toe Olive
Poseidon's Fury Iffy for the 2 yr old, DD slept thorugh it at 3, liked it at 4)
For the older 2
Spiderman (my DD's favorite at 4)
Dudley do right
Popeye and Bluto's BileRat Barges
Jurasic Park river adventure
Hulk and Dueling Dragons maybe for the 8 yr.