Well it sounds as if you've made your decision but I would skip AK. Other than Kilimanjaro, Festival of the Lion King and Nemo's musical, there isn't much for children that age. Heck there isn't much for most people which is why it's almost always a 1/2 day park. Epcot is such a nice, peaceful change from MK with its crowded walkways and constant stimulation. Epcot is wide open, fun and educational.
This is exactly why you need to know what appeals to your family. There's plenty do at AK to last a full day. It's not a half day park. It's a half day park to the above poster's family. There is a difference.
There are more attractions than just the 3 named above appropriate for the 4-7 age range. Will your children or family like them all? maybe not, but that doesn't mean there aren't options. We could never do AK in half a day. We never fit everything in in a full day.
And for kids who love animals, good luck dragging them away. Especially if they make it to the petting zoo or get caught up in completing the wilderness badges. That's a half day there alone to do both of those. Add in a few shows, a couple rides, the parade, and maybe a sit down meal, and you definitely have a full day.
It's Tough to be a Bug! - can be too scary depends on kid
Festival of The Lion King - child must be able to sit for a show
Kilimanjaro Safaris - animal safari in cars
Wildlife Express Train - train ride to petting zoo and veterinary building
Affection Section - petting zoo
Conservation Station - educational exhibits and veterinary
Kali River Rapids - very tame raft ride compared to others of its type, might be too much, might be ok
Flights of Wonder - live bird show, kids need to be able to sit for a show
Finding Nemo-The Musical - kids need to be able to sit for a show
Fossil Fun Games - carnival games with prizes
Wilderness Explorers Badges - hands on activities spread throughout the park the kids can earn badges for participating in, some are more fun or more interactive / complex than others
Primeval Whirl - crazy mouse ride
The Boneyard - playground
TriceraTop Spins - Dumbo ride
The Parade - I like this parade best for little kids, it is very interactive, the characters will dance with the kids, and you get much closer up for a more personal experience because there aren't big floats but these crazy puppets and stilt walkers instead
Character meet and greets
Character meals - Tusker House you can early entry buffet breakfast with Mickey and pals or for a little more exotic food lunch, fun parade for kids to participate in with drums to beat
Rainforest cafe
Animal viewing on the trails - many different zoo enclosures to view animals throughout the park, some designated animal trails, the Wilderness Explorers Badges are spread throughout these areas and give you interactive things to do and facts to learn that go along with the animals you are seeing