Here's some pixie dust for a great trip. Sounds like you deserve one and your DS deserves a 5th birthday full of fun.
Not a dumb question at all!
And you are not even the first one to ask, so whatever other questions you can think of, go ahead.
You don't need a letter from your doctor to rent either a wheelchair or an
ecv (
scooter). At the parks, the scooter and wheelchair rental is first come, first served, with no reservations. Except in really busy times, there isn't a problem with getting wheelchairs (from what I've read; we don't rent because DD has her own wheelchair). Scooters are limited in number and one may not be available if you are getting to the parks late or park hopping.
Here's a
link to the DIS page about touring with mobility disabilities , which includes info about renting at the parks.
Many people choose to rent from one of the outside medical equipment renatl companies. Heres a list of the ones DIS posters have reported renting from:
Care Medical:
http://www.caremedicalequipment.com/
Walker Mobility:
1-888-726-6837
www.walkermobility.com
RANDY'S Mobility is in Kissimmee 407-892-4777
http://randysmobility.com/
Colonial Medical
http://www.colonialmed.com/about_cms.html
The advantages to renting from one of the outside places is that you always have the wheelchair/ecv available. It can be quite a walk from parking or the buses to where you rent in the parks (there is a trial program with wheelchairs to go from parking to the park entrance). Also, you would have one for the resort and DD where you can't rent.
A lot of people prefer a scooter because it gives a lot more independence. It would be especially helpful with a 5 year old not to have someone needing to push you in a wheelchair. They would have a hand free to hold his or push him in a stroller if needed.