I used to do small picture albums but the prints often came back in the wrong order, so I went to website and made sure they were watermarked. They still ended up on FB with my watermark on them.
A contact sheet is a good idea, the only downside would be that the parents cannot see the kids expressions. Eye open etc etc
I would also print off one of your own choice at the size you are looking to sell so they can see the quality. Put the print in a nice mount and it will look even better.
Try doing the team and a single print on a 10x8 or 12x8 with name, age group and year on it.
Personalising it will make it more attractive.