OP, couple of suggestions I stick a pillow from sofa in the MW and it keeps the glass tray from rattling, bouncing around and doesn't take but a second. I have had 2 rear kitchen TT's and never had a microwave come open, even though I have to jump the curbs to park at home.
Second suggestion is to plan meals so that you don't have to cook or go out for dinner when you are traveling. I try to cook ahead at home, things like chili or a casserole, so I only have to heat up on travel days. I also try to put a couple of convenient frozen meals in freezer for ease in stopping. Take the time to look at the frozen food aisle carefully, you can find some that are surprisingly good and even healthy. Some of the bagged ones that you just dump in a pan for 15-20 minutes are my favorite.