Epcot is my 8 year old daughter's favorite park. It has been her favorite from the first trip. Epcot's reputation as a dry, educational park is outdated and just plain wrong.
This is just my opinion, but AK is pretty lackluster compared to the other parks. There are only a handful of attractions that interested us - only enough for a morning, really. We're in no hurry to go back to AK.
If you're staying for several days, I would say definitely go to AK. But for one day only, I'd steer clear of that park. AK has its fans, but whenever there's a poll here of what's the least favorite park or ranking the parks from favorite to least, AK is always bringing up the rear.
Again, just my opinion ... for what it's worth.