Before the thread goes into the usual pool-hopping death spiral, here's the deal with guests of guests at Disney resort pools.
Disney official policy is posted on the WDW site:
"Please note that pools are for use only for Guests of that specific Resort hotel."
The same policy is posted at all resort pools.
The better (fancier) pools do random resort ID checks in the pool area. If someone can't produce an ID for that resort, they are told to pack up and leave (a.k.a. "the walk of shame", thanks chalee94
). YC/BC checks ID before you even get into the pool area.
If the pool is not busy, if they're asked, lifeguards will very often allow guests of guests to swim.
Now, it's certainly possible that no one will ask for ID at the pool. That does happen. It's also possible that every single member of the party will be asked for ID, including all of the children. That happens too.
If it were me, I'd simply explain the situation to the lifeguard and ask if my guests can join me. If the pool's not busy, there's an excellent chance they'll say yes. I'd much rather get it sorted with the lifeguard ahead of time then take the chance that my guests will be asked for ID, and told to leave the pool.