Explain why you are doing the car wash and accept donations. Publicize this with the congregation as well. Manual Labor Auction . Use a flat rate or auction them off. Rent them on a Sunday and have them work for the people the next Saturday.
Kids are usually more comfortable being auctioned off in pairs.
CD and Tape sale. PO Box 572, Crossville, TN 38557. Confrontation Point Ministries. We are a Gospelcom Alliance Member.