Oy...you have my sympathies.   I directed 11 teens in a show that I took to my first drama festival and I never had all of them there, even for tech reheasals.  The only time I had them all was for the festival performance and the normal run of the show.  No I take that back, there was one perfomance where I had to subsitute for one of the teens.    Bribes, threats, begging, pleading and being nice never worked.   The parents?   Aahhh faghed about it!

When I have directed BCPE I always asked the moms of the baby angels to help back stage. They can rotate shows so they all only miss one show. Put one of them in charge of the schedule.  You have enough to do. This helps with keeping the noise level down in the green room and it also places them back there to help with the baby angel's costume change, which needs to be pretty quick.

Speaking from experience, asking the parent of the kid who isn't behaving to help is like asking the wolf to guard the chicken house.  He isn't behaving because she (they-the parents) have never taught him how to behave. Never expected him to behave. Ask the parent of the best behaved kid to help back stage.  Works much better.