Portable panels will probably walk-off while your gone... unless you take them home with you.
When putting more than 1 horse into the same small pen
, I would do round if possible. That way a horse cannot get trapped into a corner.
If you will travel there often, I would think the run-in shelter with 2 stalls would be the best, but would cost more.
Trail riders and endurance rider sites will have all kinds of travel type fencing that you could use if "best cost" is the issue. Test them out at your home stable first before traveling.
Since it is a hunting camp, post & rail might be the most cost effective... if you can find a "lumberjack" to help you build it!