Here's information about renting wheelchairs and scooters (
ECVs). All of these companies are ones that DIS posters have reported having good experiences with.
Care Medical:
http://www.caremedicalequipment.com/
Phone (407) 856-2273 Toll Free U.S and Canada (800) 741-2282
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
(800)747-0246
http://www.scootaround.com/ Not much feedback. Several people who reported they had no problems.
Randy's requires that someone be there for delivery and pick up. They will expalin and demonstrate it to you at that time. The rest will deliver to Bell Services and leave it for you.
If he's not so hot right now about renting, you might want to take the contact info with you in case he changes his mind. WDW is huge - just the trip around World Showcase is over a mile! You can rent ecvs by the day from the parks (same place as stroller rental), but they are limited quantity and there is no guarantee they will still have any when you get there.
Information about GACs:
You can go to Guest Services in any of the parks and request a Guest Assistance Card (we call them GACs to avoid typing so much). In general, people who use wheelchairs or ecvs don't need and won't be given a GAC because just having the wheelchair/ecv alerts the CM that they need an accessible entrance. If that meets your needs, you don't need a GAC. But some people need a quieter place to wait, a place out of the sun, a place away from other people or to be able to bring a stroller into line and have it treated the same as a wheelchair. The GAC is a tool to alert CMs of that sort of invisible need. It is not meant to (and usually won't) shorten or eliminate your wait in line.
To request a GAC, go to Guest Services in any of the parks with the person with a disability and explain your needs. Just saying, "I have _ _ _ _" does not help much, because some people with that diagnosis will have minimal problems waiting in line and others will have lots of problems. You need to be able to explain what sorts of behaviors/problems you expect to encounter. The GACs have different messages stamped on them, depending on what the needs are. GAcs issued in one park are good in all parks and are usually valid for your entire length of stay (You don't need to get a new one each day).GACs are usually issued for the person with a disability plus up to 5 members of their party - there may be times when you are asked to split into smaller groups because of attraction capacity in the special needs area for that ride.
Another way to shorten your wait in line is to use Fast Pass. For attractions that offer fastpass, you put your park tickets into the fastpass machine and a fastpass pops out for each ticket. One person from your party can run ahead with all your group's park passes to put them in the fastpass machine (each person doesn't need to do their own). There is a return time printed on the fastpass and when you return, your wait time is going to be 15 minutes or less. That allows you to wait inside, somewhere cool until the return time.
Also, getting to the parks early helps a lot. That way you are going when it's cooler and less busy and by the time it becomes busy and hot, you can be back at your pool swimming. Then return later in the day when it's cooler and people have left the park.