Wow!
Seems like you guys are in a difficult position. The best policy is honesty. I would have the entire team, hold a meeting with these parents, to fully express how you guys feel about the way they are "running" the team. Use constructive criticism in order to reach a better understand of each other's feelings, and how to help them make better decisions for the team. If it all goes SNAFU, then mention that if they are not willing to cooperate and work together, the team will look for a new mentor, or head coordinator. Hopefully this will help you.
"When everybody works together, we all win."
(I forgot who said this, I wish I could give him/her credit)