My daughter was born with a major birth defect which later caused Scoliosis. When we took our vacation in '97, it was a few months before her back surgery. SHe was still able to reach over and touch her toes despite a 60 degree curve, but she couldn't even walk the length of one of our malls here (about average size), without having to sit down and rest. Her endurance was nil.
After her surgery, two years later, she did real good at a local theme park here in Alabama.
However, four years ago, she had a mild stroke after surgery. Then spent three more years just barely able to breath due to the shape of her face caused by her birth defect. Well she had surgery last year for that, but she still has no endurance after all of that. Will we feel bad about putting her in a wheelchair? Nope! We know that that may be the only way she can enjoy herself without wearing out after long treks through the parks. We didn't worry about her jumping up out her wheelchair then, and won't worry now.

If your son needs the wheelchair, and/or tires easily, definitely go for one. I'm sure now is stressful for you guys, so take a load off in that area.
Sorry for the long post!
(peeking around for Pop Daddy)
Kim