I fixed a cheap jam box to run off of the 12 volt cig ligther on the bus. This worked wonders!! We recorded a few tapes of Southern Gospel Music and played them all the time at about 75% volume. It gets them in a better mood before church and on the way home.
When church is over go straight to the bus with the kids. The kids running around playing after service gets their blood pumping and they are more likely to be rowdy on the bus. Don't allow no one else to come on the bus once this is done but the people involved on the bus itself and the kids. Allowing the pastor to say something to them changes the authority to him which of course he then gets off the bus and the authority goes with him which leaves you with a problem. LOL