Congrats Bernie - Grand dogs are great - when they become trouble you give em back.
Is there a safe open paddock where they can all run together when you do the first intro. Off lead intros are good to see how ' the dogs will get on. In an enclosed space, or "their space" they may get a little protective - maybe.
I would empty the pool but large bones are ok as long as they cannot be cracked and split open and splintered. Maybe cut up some blue line mains water plastic pipe (from your local hardware store) just to give them all something to chew that is safe.
Not sure what you are after in the last part of your post. Can you elaborate please.
Border River Pet Resort