There is no wrong or right way to do this. Like said, it's totally what you're comfortable with!

For myself, I'm only allowed 4 children so I usually only have 3-4 children at a time....totally manageable even if they do act up. The way my dc is set up, the other parent wouldn't be alone with the children. Even if I'm in the room though, they are still able to say something that I might not. Same goes for when we go out to play dates, play groups, mall, restaurants etc. again, just my opinion, but that is too much bubble wrapping for me and isn't my style so my current families know that already

It's all about calculated risks and will be different for everyone