You can't "keep part of their deposit", because Airbnb doesn't hold a security deposit from guests. It's only there as a threat that it could be charged. If you want to charge a guest for damages, you have to first send them a request for payment, and if they refuse, you then have to try to get Airbnb to pay, which is no easy task.
If guests are behaving in a way that isn't right, you should address it right away. Send them a message telling them the ring doorbell kept pinging on your end, so you saw the child going in and out, which is fine, but then him banging the mail slot and the playing with the ring bell, and some water being thrown out of the mail slot, which is a concern for you to have water thrown about in the house, as it could damage your floors and furnishings. Try to be tactful, as in "I know kids will be kids, and I'm glad they're having a good time, but I would really appreciate you keeping a close eye on them and not letting them play with things they could damage or throwing water around unless they are outside."
@Jill963