My kids (6 yr old boy, 4 yr old girl) like thrill rides, so we use them for the long waits - Splash Mountain, Seven Dwarfs, BTMRR.
What time of year are you going?
For the lower key rides your kids might like, these rides can have long waits on busy days:
MK - Buzz Lightyear, Dumbo, it's a small world, Mad Tea Party, Winnie the Pooh, Peter Pan, Little Mermaid (you really need a FP for Peter Pan)
EPCOT - Spaceship Earth, Nemo, Frozen (duh, you need an FP for Frozen)