I believe the discount you're referring to had to be booked in Sept. You could do a search & check the thread for certain. There was also talk of it only being good for residents of certain states.
Yes...there is a discount for AP holders. It is $35 off any racing package & $25 off the ride-a-long.
I also know a couple of years ago, the Orlando MagiCard offered a 10% discount.
If the driver has done an experience at another track, you also are eligible for a return visitor discount (maybe 5%-10%).
You must mention the discount when booking.