Hi Jennifer,
I love that Disney has given guests an option to renting strollers by being able to purchase them on property. The ones for sale are the single Kolcraft Tour Sport Umbrella model which features a sunshade and a foot rest. I can't remember if the ones they sale come with a cupholder or not but I do remember there really wasn't any storage.
You can find pictures of the Kolcraft Tour Sport Umbrella Stroller online to get a better idea. The strollers are available at most resort shops and within the parks. I've also seen them at Downtown Disney in
Once Upon a Toy although there may be other locations that sale them as well.
When I was down there in March, they were selling for $49.99 plus tax which seems to be the average retail price. The specs I saw online for this model showed a maximum weight of 35 lbs.
If you decide to buy a stroller when you're there and don't want to travel home with it, you could always find a family checking in when you're checking out and spread a little pixie dust to start their trip by passing the stroller on to them.
If you think the Kolcraft may be too small for your son, another option is to rent a stroller from a local vender.
www.orlandostrollerrentals.com has a nice variety of choices and will deliver to your resort. In fact, its usually waiting for you when you arrive.
Wishing you many magical memories :-) Allison