No flaming here... Just facts, okay?
You can not exceed the capacity of a room. If you are in compliance with the capacity, you are okay to bring an air mattress to accommodate your party's need for separate sleeping surfaces.
Particularly if you are renting points, you need to follow the rules of the resort. You can cause significant trouble for the owner and yourself if you are caught breaking a life safety rule (capacity.)
Just a quick note of warning... This is not in the same category as using your refillable mug from 8 trips ago... Violating the capacity is a major deal and they will require you to get an additional room at the full rack rate. If you refuse, you would be asked to leave the resort.