Congrats on your trip!!! I have used DLP's version of a GAC card in the past. In theory, it's supposed to work just as at WDW. The thing is, though, that's CMs are not as used to people having a card like that. At some attractions, I couldn't even find a CM to ask or let me in through a separate entrance - sad, but true.
Also, since my disability isn't visible, I was subjected to some very rude comments from other visitors which I've never experienced at WDW (unfortunately, Europeans can be like that sometimes...).
That being said, if you're in a scooter, I'm pretty sure you'll get the necessary attention you deserve. If not, make sure to speak up! Also, since you're going during a slow time, you shouldn't have any trouble with fellow visitors. You may not even need the GAC in many cases.
Have fun planning your trip!