Need some advice about hiring scooters / wheelchairs at the various theme parks, Dad doesn't want to hire one for the duration of our stay at the Boardwalk, said he would consider hiring something for the day when we get to a park, if he needs it (he doesn't want to admit that he might need the help). Can you order on line or do you have to wait until you get to the theme park? Any idea of cost?
Burnice; hop on over to the disABILITIES part of the DIS. All the info you could dream about is there in the stickies on the top. It includes prices, phone numbers etc. etc. Offsite rental can be done beforehand online/phone, onsite can NOT. That is first come, first served and they can and do run out.
If he can navigate one; opt for the
ECV. It gives him freedom to move about without having to need a helping hand. That's a big thing for any person and even more so when they are reluctant to give into the fact that they can not do a park without a type of aid. With that he could travel back to the hotel earlier if he wants to without feeling he has to "rain on your parade", grab himself something to eat from the boardwalk, run and get your mom a cup of coffee, just do whatever he feels like doing. They do take some practice, but are pretty easy to navigate. If possible; offsite rental imho! It's cheaper and the ECV's are easier to navigate (3 wheels have a smaller turning radius than the huge 4 wheel ones that WDW rents out). Also it comes with real independance instead of him still possibly having troubles with distances at the boardwalk after a long day or getting back to the busstop after hitting the parks.
Have him try one out at one of the malls at home. Obviously each brand and type comes with it's own little caracter but I've found the basics of being able to navigate one to be pretty darn close for whatever brand or type you use. It would also give him some time to get used to crowds and feel confident enough. If he's worried about getting it on and off the bus; you can do that for him if desired.
If you find you need to opt for wheelchairs, again; offsite rental! Cheaper and much better material. Those rental onsite chairs are just......bad. Great that the option is there but they are beaten down, uncomfortable etc.
Small tidbits; bring along a cushion he's comfortable on to make a rentalchair more comfy. Also bring along something like a towel, breathing cotton or something alike. The sun is brutal! Most seats are black, can you imagine sitting back into the chair/ECV after it has been out in the sun? Not just that, but sitting down for a long time in that heat can cause you to sweat. The materials used in rental seating for chairs and ECV's are non breathable and will stick to you in bad nasty feeling ways in the Florida sun.

A simple piece of comfy fabric draped over the seat and back solves that immediately.
If he has any worries about what others might think or whatever; tell him he should not. WDW is set up for him to do whatever he can do but to use help wherever needed. It is perfectly OK to use an ECV for instance in the parks but not in the lines if he can still navigate those without. Just park it outside in the designated areas, enjoy a ride or show like normal and use the aid for transportation. If he can not; by all means take it along!!!!!!!!! That's what they are for. He can transfer out of it when it's his time to ride. Or if better suiting his health; in some rides he can stay in a wheelchair and ride. This usually adds waitingtime (few carts available), but use the option if it's better for him. An ECV does come with the need to transfer to a wheelchair for a larger amount of rides/shows. The specific list can be found at the disABILITIES stickies and it's clearly marked on parkmaps and CM's working the ride will also help you out there.
As far as proud goes; proud is great but do not let it become stupidity. Stopping oneselve and/or there loved ones from doing what they could've and/or would've done if his health would've allowed it, is just stupid and silly. Tell him I said

there is a huge amount of pride to be found in honoring your body and health and not ruining it. That there is more pride in respecting ones own limitations. Using an aid is just that; using something for ones benefit. It is not a ride of shame, it is a ride of smart. And do the harsh math. A typical WDW day comes with 10 miles a day. Can he do 100 miles in 10 days? Heck, can he even do 50 in 10 days? If no is the answer or "yes, but it results in..................... (pain, whatever), that is a clear sign he will benefit from an aid. Brookdad, take it from a too stubborn 31-year old; ignoring yourself any aid that you could benefit from will only result in a worse trip than using one ever can. The difference can be heaven or hell.
If you find you need help or something while onsite; ask around. CM's are wonderfull in helping when it comes to needs. Also feel free to contact myself if I can be of any help. I'll be down at WDW for 14 nights, so I'll be there for your whole trip. I've done WDW both solo and with others and use a chair 24/7 (at WDW that results in a powerchair anywhere outside of the room). I'm not unfamiliar with being more stubborn than smart sometimes

and have been through the process of having to deal with declining mobility. Heck, if that's what would be needed to have him be OK with using some help, I'ld happily do some parktime or boardwalk time with him to "hide behind" me and see first hand how it also can be instead of struggling during the day more than has to be.