My DDs were 10 and 7 last year, and I just posted about DD8 (then 7) on another thread, so I'm copying it since I am lazy that way.
My DD8 was seven and a half last summer when we went, and she liked IOA better than US, but she liked them both. She liked Seuss Landing (Cat in the Hat, One Fish, Two Fish, the trolley train ride, and even the Caroseussel), Flight of the Hippogriff,, Dudley Do-Right, Jurassic Park, Popeye and Bluto's Bilge Rat Barges and Storm Force Acceleratron at IOA. She didn't do the big coasters, Forbidden Journey, Doctor Doom or Spiderman (she rode Spiderman when she was 4 and was terrified - she still won't ride it ).
At US, she liked Disaster, ET, Jimmy Neutron (closing, but will be open some of the summer), Shrek, Woody Woodpecker and the Curious George play area. She did not like Men In Black, Twister or Jaws. The Mummy was closed the day we went, but it is not really her kind of ride.
My DD10 loved everything, although she did not go on any of the big coasters (Hulk, DD/DC, RRR) - the only upside down roller coaster she will do is Rock n Rollercoaster at Disney since she can't see the loop.
I think you might be proven wrong, OP, about not being interested in IOA.

I think Seuss Landing is one of the best-themed lands in all of Orlando, and to me, the attention to detail blows Fantasyland at MK out of the water. I love being there and riding the rides. I always tell people not to skip One Fish, Two Fish - it is infinitely more interesting than Dumbo, and I'd download the theme song to my iPod if I could find it!

The WWOHP is so beautifully done - it is not perfect, but once again, the attention to detail for a HP fan is breathtaking.
Hope your whole family has a great trip!