A Guest Assistance Card (GAC) is used at WDW and now
Disneyland. There is a major difference between a GAC and the former Disneyland Guest Assistance CArd.
The purpose of a GAC is to provide information in a semi-standardized form to CMs where the person has an invisble disability. This might be for a child where there is need to use a stroller as a wheelchair, or a need to stay out of the sun, or a vision or hearing problem.
Also, a GAC should be requested at Guest Sevices of the first park attended; it is good for the length of stay and for the person with the disability and no more than five additional people.
Note that at WDW almost all attractions are "mainstreamed" and either a wheelchair or
ECV can go through the regular lines. It is NOT designed to bypass waiting.
There is no requirement for renmting an ECV other than having the money to pay for it and having them available. As a user, I would strongly advise two things
1. Rent an ECV rather than a wheelchair. It will allow for more mobility and dad will be able to drive it himself and not feel that he is a burdon on the rest of the group.
2. You are better off renting from off-site rather than from Disney. I am not responding to this from at home; sometime later today or tomorrow I will post my standard blurb on
ECV rental which lists five good off-site rental sources.