Excellent age to go,depending on the kids... Do they like disney? Make sure they watch a few disney movies etc. before they go.. They will know the characters and won't be scared of them.   Can sign up for breakfast with disney,it is a one on one chance to meet the characters. Stay on a disney property if you can .  A few more bucks extra money but worth it for transportation and the things you can do after you get back to the room. Swimming pools,arcade and places to eat are all within walking distance. Good security,no traffic. Mostly stay in fantasy land,save the others for later.Depending of course how long you are staying. Epcot is too advanced for 7 and 4 in my opinion.

   Took the kids and grandkids 2 years ago they were 8 to 4.  Had a very good time. Spent the day there till kids were tired. Went back to room on bus,played around pool took naps and took bus back for fireworks.

   go for it

 Also try to get appointments on the most popular rides..   Doesn't hurt to go right to the back of the park and work your forward.  Helps beat the crowds that start in the front.   Tuesday is the least crowded from what I hear.  Try to go later if your not staying till the last parade. Kids will be very tired if you go early and stay till the end.  One of the benefits of staying on a disney property.

    That all said the wife an I got one of those condo promotions one year had to listen to a hard sell for and hour. Stayed at a classy resort off campus. three swiming pools and all the goodies. 39.00 dollars a night.Had a whole house to ourselves. Course with a couple of kids I wouldn't do it.