The best thing to do is call where your reservations are and tell them you are a DC member. They usually ask for the member number, and you have to show the card on check in. Supposedly your discount does not always apply, or can be different amounts at different times. I had one reservation changed 3 times. First was 47 noc for full hookup at campsite, then I called and got 37 noc for DC discount, then called back a third time to get an AP discount (3rd and final price of 31noc). The opinions on the board here seem to be to get the reservation first for when you want it and then play the rates game. Good luck.