DD 7 went to a pool party a couple of weeks ago and I did just drop off.
But I knew the mom had hired a couple of teens who are lifeguards at the local waterpark to work the party and there were only 8 girls (including the birthday girl) attending.
I think the kids were much safer at that party than at the nieghborhood party we went to on Memorial Day.
Plenty of parents around, but no one specifically assigned pool duty. I swear some parents had no idea when their kid was or was not in the pool area. Crazy!
I hope the sibling thing works out for you.
I think it's incredibly rude for people to bring siblings who were not invited to a party, but it does happen, and it's probably more likely to happen at a party that parents feel they need to stay for (like your pool party...sorry)
The last time I had the sibling issue come up I told the mom that little brother was welcome to stay and participate but that I only had enough prizes, goodie bags, Baskin Robbins clown cones etc. for invited guests and asked her if he would be OK with that.
She didn't leave him.
I hope the party is a great success!