DD was 4 (getting close to 5), on our trip last December. It was her 4th WDW trip, so she knew what to expect. She is a kid who has not sat in a stroller at any time since she could walk at 12 months EXCEPT for at WDW (I'm talking not even at the zoo, big mall, etc). DH asked her if she wanted to leave the stroller at home for the trip. She looked at him like he was absolutely crazy and said in her best sarcastic 13 year old voice "UHHH NOOOOOOO". I would say if your DS whined a bit about the walking at the Mall of America, he will definitely need a stroller at WDW. If you think you can resell the double when you get back, it might be a good choice, but realize that the strollers can get dirty at WDW and they can get beat up on the planes, so it might not be in perfect condition after your trip. Also realize that every time you get on a Disney bus, you have to fold and hold the stroller. We don't have a double side by side, but I would wonder how hard it it to fold, and whether it is going to be too big and bulky for you on the bus when folded. If those things are going to be a problem, then I might just buy a cheap single for him (of course then you are dealing with 2 strollers), or look into renting the jogging stroller as suggested.