If you use traps, put them where the mice/rats path, along the corner of the wall. That way, even if they don't stop for the bait, they will still set the trap off. I recommend "JAWZ" snap-traps.
I don't like seeing animals suffer either. However, it is self-defense, because they foul up foodstores and bring in diseases (hantavirus), so one has to do something. Spray foam and stainless steel wool (so it doesn't rust) do work, but once they decide to move in, you have to do something, otherwise they will destroy your rig with their filth and gnawing.
JMHO, the best way to get rid of mice is well stated in the first reply. Nothing like seeing a cat walk out from under your RV with a fat rat in its mouth.