We were there last week. Armbands are various colors and types. They do check IDs when you get towels, but they also roam the place and look for people without armbands in the pool, sitting at tables or lying in chairs. They checked all our IDs and not just one. They check real good in the afternoon when more people leave the parks and hit the pool.
Everyone has a room key and that's what they want to see - teens, younger kids, older folks, everyone. The pool is reserved for YC/BC/BCV guests only.
They did ask a few people to leave when they couldn't produce the ID. They also have ways to check out your ID if you don't have one handy.