Dear D.:
My two daughters were about the ages of your boys when we took them to DisneyWorld.
Some of the meals with the Disney Characters we booked before the trip. That was a highlight!! We dressed our girls up and took a lot of pictures, and the pictures stay mounted in various rooms of our home.
There is a restaurant called the Coral Reef, I believe, where you are eating in a restaurant and the aquarium fish are staring at you.
You can be sure to get an early start in the morning before the crowds would come. Pace yourselves to go back to the room around lunch and rest by the pool, or in the room. Then you are ready for the afternoon (2 pm approx.) to start afresh into early evening.
Another restaurant/show that was a delight was The jamboree, the 3 yr. old may not last. (We booked this restaurant in advance, also.)
Don't try to see and do everything, but pick out the highlights of what your family will enjoy and just enjoy the gift of each other in a wonderful place to be.
Don't push the 3 year old into anything he's not ready for. The 3 year old stage, you will remember, is the time of nightmares, and you don't want any of those destroying you rest. The other thing that I might recommend is the you bring handi-wipes for cleanliness of those little hands.
If your guys have flown before, you will know if they are sensitive to the air pressure in the cabins....if not, check with you pediatrician and ask what he/she recommends. The 5 year-old might be able to chew gum, but the 3 yr old is really the one in question.
D., enjoy your family and have a wonderful trip,
E.