Short answer: Master lock trigger lock with a combo is less than $20 on Amazon.
more info...I have a Fort Knox and Gun Vault. The ft Knox is a serious security box but not quite a safe. The gunvault could be pried with a screwdriver. Neither are light enough for backcountry.
I had one other one with an electronic lock that failed a few years ago. I imagine they are getting better but it made me wary of the potential for lock failure.
If you are looking for something portable, I tend to like trigger guards with a combination lock or cable locks also with a combo. No key to loose. A lockable pistol pouch might be another option.
I'd keep it on you, and when you're sleeping in the tent if you're really concerned about the kids messing with it I'd just pull the magazine and clear it. Then keep the mag in your sleeping bag or somewhere you can access it.
I bough a small Pelican case for flying/travelling.
Even left my Glock in it at the hotel office when we drove
over into Canada once. Padlocked of course.
I have a couple of these for in home but they are too heavy to haul around. Fine for in the truck or tent when truck camping. If hiking in, it is safest in a holster on your person.