We have had to relocate for my job several times and the movers have never failed to "lose" something, a small TV, stereo components, take your pick.
I have always packed the trains myself, using original boxes (as you propose) and then rented a truck and driven trains and train layout to our new home. Perhaps I have been fortunate, but I've had no problems with the truck parked in a motel parking lot (knock on wood). As John noted, I've made certain to back the vehicle in near the door to the motel room. I use a good heavy duty lock on the rear door of the truck and will also "temporarily disable" the vehicle so that it can't easily be driven away. I know this is bordering on paranoid, but better safe than sorry.
Good luck with your move and hope you enjoy Jersey!
Curt
