Hi, Allison! My daughters range in age from five to almost 19, and I think the best times we have as a family are at the Magic Kingdom. Everyone enjoys the classic attractions, like the Haunted Mansion, Pirates of the Caribbean, and the Jungle Cruise. Now that my five year old is tall enough, Splash Mountain and Big Thunder Mountain are must do attractions for us. Your oldest son might like a spin himself on Space Mountain!
You will also find Buzz Lightyear has a wide appeal - my girls like to challenge each other to get the highest score. They also like the Mad Hatter's tea cups - not so much for the girly colors, but because they like to see how dizzy they can make each other.
Alternatively, EPCOT is also a great theme park for all ages. Your seven year old is probably tall enough for things like Test Track and Mission: Space; and my girls could spend all day at Innoventions. Other popular attractions there include Soarin' and Maelstrom.
You might want to check out the planning tab at
www.disneyworld.com and let the boys make a list of things they would want to see if they were going to each theme park. Then based on the length of the lists, make your decision to go to the park with the longest list of attractions they want to see!
Have a great time!