There is no reason why the 2.5 yr old can't sit at the table by herself and eat .... Put her there everytine and be firm and eventually she will get it ... She might not eat a few times but she will eventually realize if she is Hungary and wants to eat this is the way it's going to be done. Talk to the parents and let them know that you can't possibly have her sitting on your ones while she eats and encourage them to make sure she is sitting in her own chair at home for meal times.
There is also no reason why you shouldn't have some break during the day ... Even school age children can rest in the afternoon ... They can lay on the couch with a book or watching tv... Let them know they are not to move from that spot or the tv or book will not be an option .... You just gave to set the rules and stick by them..... I don't allow drop off or pick up during quiet time .... So let the families know that mid afternoon drop off is too disruptive and they need to be there for 12 (or what ever is acceptable to you) gives you a chance to get them settled in and down for naps .as for waking up during nap.... I have one that started with me at 22months and had no schedule at home and climbed out of playpens ... So everytine he climbed out I went in and said no climbing out and I would put him back .. I kept doing it over and over and finally he stayed in ge also didn't sleep very long so I would go in and say it's bit time to get up yet go back to sleep or lay quietly....now if he wakes uphe just lays quietly until I get him .... But u was firm and he knew I meant it. Filling spots is hard the first year but it will come. Good luck