Yes, you can use a GAC, but in my experience, that does not mean that you will get a seat. there are benches (sometimes - sometimes the benches are in the back of wheelchair sections with all the wheelchairs in front of them). If you must have a place to sit, I would look into renting a wheelchair even just for the evening.
And you must still have a fastpass for every member of your group to use the wheelchair viewing areas.