Leave, but only after explaining why.
You are not letting the kids down, the denomination is. Maybe your witness to the truth (calmly, with love) may inspire others to live their Christian faith better. Maybe others agree and just need you to speak up first. Or maybe they disagree and it will become clearer that there is nothing more you can do. If you find another church, there will be children there who need you, too. If you keep doing the music for the kids where you are and do not air your concerns appropriately, they will more likely grow up as mistaken as their parents.
Also, pray before you say anything, so your words will be Spirit-filled.
Best wishes.
Great advice to Dengar...
Your testimony is to Faith in Christ...you will be an inspiration to those kids.