ugh!?

I am not good w/ older children.  on tuesdays I volunteer to do childcare for parents who attend a class at our church.   I started out w/ the smaller kids, ages 2-3.   That I am good at….tonight there were 14 kids, ranging in age from 4-12 and there’s another childcare worker, she’s 17 and is about useless unless you tell her exactly what needs done, I think she’s used to being the kid and doesnt necessarily want to be in charge…at that age I was already taking lead teacher roles…differences in personalities I suppose. Tonight I had to tell her that her conversation about piercings was inappropriate, the kid on her lap at the time was 5!! and no it just wasnt about ear piercings.  but I digress.   soooo next week I am going to be more prepared.  we spent a lot of time outside tonight but the time before and after that was a little chaotic.   any ideas for crafts w/ multiple ages.  like I said younger kids even up to age 6 or so is fine, but older than that I get lost on what they need/want to do.   I think I’ll do a craft w/ marshmallows and toothpicks, take some homemade playdough and maybe one other activity to add to see how it goes.   I like order, and I know kids need it.  So I’m bound to make this easier for me and them, we spend 3 hours together, I need something to keep from getting bored.  the older girls got really bored today,I might bring some jewelry making stuff for them, or make them help the littler ones w/ crafts.   any other ideas??