I wouldn't spend the $900 myself. I would have something at home in the backyard--simple bbq or catered by a grocery store, get main dish from a restaurant, etc.--as it would be a lot cheaper. I would have it all ready to go the day before except for the main entree, But, that is me.
People have parties around here, but usually in their homes and not nearly as elaborate as some of you have described. Must be the area.
If you do it at D & B's then I think you should have power cards for the kids and $10 won't go very far or last them very long! Plus someone will have to go and supervise the kids.