Not sure if they still do this, but we went to DQ after 5pm and they had a sign out front for half price admission. If you plan on just checking out, it might be a good option so you don't pay full price for the third person.
If you are not planning on going with your husband and teen you have to show id with the coupon of the person that the reservations are made in at your resort. If they are made in your name and not your husband then you have to be there to redeem the coupon. We ran into this in July. My two teens took the coupons to go and we went shopping at the other end and got a call from them saying I had to show id.