I was just there, although for an overnight stay. I'm saw information (in the 'hotel book' in the room) giving rates for various late-check-out times, and I think there was also a 'day use' rate there.

I was given a complimentary late check out to 3pm, "due to your Diamond status".

All the staff I encountered were extremely friendly and helpful, and I would be very surprised if you were hassled for having 4 people in a room. Might be a tight fit somewhat though, I'd get a 'deluxe' room for that if I were you. (On the 'outside' curve' and a bit bigger).

The 'baths' part of the locker room was great for relaxing, BTW. At least on the ladies side!
There's great big indoor pool also, but bear in mind that you require a swim cap to use it.