IMHO, a little common sense goes a long way. Contrary to BF lore, there aren't roaming gangs of mechanized bike theives, just waiting to steal your **** the second it's out of your sight. Most of the time, bikes get stolen from places like trailheads and public parking racks because it's a known spot where there are going to regularly be bikes left unattended for long periods of time.
​​​​​Constantly moving from place to place is a form of security in itself.

​​​​​Same goes for securing the bike when you're on the go; a little bit goes a long way:. Lock the bike to the rack to the vehicle frame. I like cables, some people prefer chains, but nothing is 100% "un-stealable". The point is to discourage the opportunists, by making it obvious that it's going to take some extra time, so maybe look for something easier.
When I have to leave the bikes on the car for a short while, I try to park front and center, where there's constant traffic and attention. Parking at the end, or around the corner will reduce your visibility, but it also can provide cover for anyone messing with your stuff. Backing up into a Holly bush is a good idea; I've used that before.
Keep your bike in the hotel room, for sure. Also unless you're traveling to an event with your "good" bike, bring your #2 or #3 bike. It'll be less painful if something does happen to it.


rosefarts a small trailer might not be a bad idea for an extended trip, with two littles, depending on how self-sufficient you're trying to be (how much stuff you're bringing with you,) it's a whole other set of considerations, but could make it more comfortable than weeks with a packed-to-the-gills passenger vehicle