All the parents come with their children here. I don't know of any drop-offs, but that is a very regional thing. I would have children of parents I knew well here without them, but not ones I didn't. Plus, the parents you know well would be the ones that helped. You should be able to drop off, but we nobody does.
Also, agree with Susan about simple, cheap and no fuss things for the kids. Save impressive and expensive party fare for the adult parties.... a few decades from now when you get to have them again.LOL