Ahh the pool hopping policy. I am actually very familiar with this being a DVC memeber and having used it myself. The ruling is, no pool hopping except for DVC members. But it's not even that simple. If you are DVC you can pool hop to any resort, except BC/YC's Stormalong Bay and AKL. If it is crowded season poolhopping priveledges are revoked. Technically you are supposed to call the resort you want to hop to and tell them you are coming and make sure that the pool area is not too over-crowded and that they can accomodate you. You will then have to check in at their front desk to get a wrist band.
As for people actually checking cards, I stayed at BCV last June and everytime we were at the pool we were asked to supply our room keys, and then they would slap on one of those paper (but the paper doesnt get wet) wrist bands.
I realize a lot of people don't agree with me, but I do like this system. If I'm staying at a deluxe hotel, part of the extra money it costs to stay there is b/c of the pool. It really isn't fair if someone staying at the POPs or the moderates could come and use the pool, make it more crowded and pay less for their hotel.
Well with all that being said I hope this clears up your problem a little. (Also if you just have children with you, you can always say that you didnt' bring their keys with you and I'm sure there will be no problem as long as there arent' a lot of kids.)