We use GAC as an abbreviation so we don't have to type so much. It is really a Guest Assistance Card. It's basically a tool to let CMs (Cast Members) know what types of assistance people with invisible disabilities need. A GAC is not usually needed by someone who is using a wheelchair or
ecv unless they have needs beside having an accessible line. (An exception to that would be children who have wheelchairs/special needs strollers that might be mistaken for a stroller; they would need a GAC to bring their stroller into line).
It says right on the card that it is not meant to provide immediate access, shorten or eliminate waits in line; and it usually won't. It will provide accomidation based on the needs of the person with a disability, which might include things like being able to bring a stroller into line or waiting in a quieter space, away from a lot of people.
A lot of people look at the GAC as insurance. If you need it, use it. But, if the lines are short and you can manage without it, save it for the times you do need it.
The GAC is usually issued for up to 6 people (5 plus the person with a disability). The CMs can make exceptions (like if you have 2 adults and 5 children, they will almost always write it for 7 people). To request a GAC, go to Guest Services in any of the parks with the person with a disability. Be ready to explain the needs to the CM there. GACs are usually issued to be valid for your entire length of stay and the same GAC is used in all the parks (no need to get one in each park). If you go to the water parks, you will need to go to Guest Services there to find out what assistance they provide.
Even though the GAC is for up to 6, there are times when you may be asked to split into smaller groups. This is usually because the space for people with special needs is small and can't accomidate your whole party or the space is needed for other people with special needs.