My kids are slightly older but we enjoyed Universal more than Disney. We did a slightly discounted Disney 4 day pass hooper through undercover tourist. The parks are so spread out I’m not sure that it’s worth a Park Hooper. There’s only two good rides at Wild Animal Park (Avatar bring one) that are extremely long lines, although there’re both fun, not sure that it’s worth the extra trip. The line to Avatar is pretty entertaining during the wait (2-3 hours). My kids, preteen, were quite bored with Epcot. Again only a few good crowded rides and the walk around the world displays and food that my wife and I enjoyed. Disney Hollywood studios will be busy, but probable worth it with the Star Wars. Also has Toy Story Mania and a Rocking Rollarcoster and the drop ride. Lots to do in a day. The main fantasyland Disney Park is mostly the same as California’s. The dwarf rollarcoster isn’t worth the long wait, although it’s designed for younger kids so it might be in your case. The Park is just packed, even when we were there in the off season.

We didn’t do any of the wet Universal (off season) but the two parks are pretty fun. Obviously Harry Potter is pretty cool as are most of their rides, although you should be able to do everything in a couple days. If they love a Harry Potter then 3 days for the two Parks would be fine.

Lines waits at Univetsal were about half as long as Disney’s, even with the front of the line spenders. Disney gives out so many fast passes that it just crippled their lines. Those staying in a Disney hotel also get to select fast passes 30 days prior to everyone else. It’s all done online now so we couldn’t even get a fast pass to Avatar or some of the other big rides. Disney feels super commercialized now, sad. It’s all designed for you to spend. Unless you’re paying up for a meal, Universal also has better food choices including a food court just outside the entrance.