Please follow the link in my signature to the disABILITIES Board for more information.
You can rent wheelchairs at the parks, but a lot of people prefer to rent from one of the off-site medical equipment rental places. It's less expensive and you will have the wheelchair all the time that way. Also, the park wheelchairs are sort of heavy, adult sized ones. if you are renting for a chiold, there are other options that you can find out about on the disABILITIES Board.