Fortunately I saw this coming a few years ago with one of my dogs jumping up into the drivers arm rest and releasing the brake button. I found a piece of 1/4" oak panel. Gave it a 1/2" wide slot with the router. It slides firmly under the brake release button and dog proofs the brakes. It is a piece about 2' square and the slot is 1 1/4" deep. When not in use it rides along nicely in the cup holder where it is not in the way of cups or anything else they are used for.
It has become habit that the spacer is in place anytime the motor home is parked.