Bama, How do you haul your bikes down to the Fort? Do you have a rack system? We pull our popup with a Jeep Commander so we do not have a way to bring our bikes. We too were out this weekend getting everything ready! 12 days and counting!
I have done it two different ways, 4PF.
On our old Jayco popup (a traditional popup with slide out canvas bunk ends), I bought a ProRac bike rack and bolted it to the front frame of the popup just like in this picture:
http://www.prorac.com/tenttrailerpro.php
Still have it if anyone wants to buy it. We had three kids so there were five bikes total and most traditional carriers only supported four bikes. (this Prorac will handle up to 6 bikes with extra brackets [comes with 4, purchased the other 2]). Just like in the picture in the link, the back wheels rested on the front popup storage compartment. Note the front wheels had to be taken off to bolt them into the front bracket (wheels went inside the door of the travelling popup) which was a pain to take them off at home, load the bikes on the frame, get to the campground, put them on back on so we could ride them. Then do it all in reverse when going home. But then again, I had two sons and that was their job. They wanted their bikes so it worked pretty well.
Then I sold my Jayco in 2014 and got my Aliner and got the hitch welded onto the back portion of its frame. For years up until 2014 Aliners had the hitch receiver on the rear bumper but the model year I bought was the first year they removed the receiver. But I had one welded on and have used it once with my normal 4-bike rack that fits a 2" receiver (kids have gone to college so we no longer number five people. So the bike rack is right behind the spare tire of the Aliner (sorry don't have a picture).
But there are tradeoffs with all solutions. With the Aliner rear rack, that puts a lot of weight to the rear of the trailer (and tilts around the axle/tires which means there is not as much weight on the hitch. So I have to make sure I put enough weight inside the front part of the Aliner to counteract the tip (Moment Arm for you gear heads) from the rear bike rack. It works but as I said I am learning the balancing act required while keeping the cargo weight of the Aliner within the axle limits.
In your situation with four people and towing a popup, I would examine the following as a possible solution:
http://www.swagman.net/product/original4-towing/ . It goes between your tow vehicle and your popup.
A Swagman towing hitch. Basically this goes into your tow vehicle receiver and it has a regular 2" ball that you would hook your popup to. But like I said, there are tradeoffs. Note in the documentation for this product that the tow bar part of the rack is only rated for 3500 pounds (because it sticks out further from your tow vehicle that lowers the amount of weight you can tow). But the good news is if you have a popup, you are likely at or under 3500 pounds for it and it also lists the standard 10% (350 pounds) tongue weight it would support.
Your tow vehicle in the owners manual or online documentation has a separate, maximum tongue weight. You should not exceed the tow vehicle maximum rear tongue weight that is loaded on the ball. So assume the bikes weigh 35 pounds each (times 4), the rack weights 20 pounds (guess), that's 160 pounds. Add your popup tongue weight (assume the maximum 350 pounds allowed on the tow bar) and that's 510 pounds on the rear end of your vehicle. You would have to check to make sure your tow vehicle could handle that.
It's a good thing you are towing a popup because this might be under the tow vehicle max limit. If you were pulling heavier trailer, the 10% max tongue weight might put you over the limit.
If I were you, I would check into this option to see if it would work. If I were starting today, this is how I would go (but I already have a heavy 4-bike rack that fits a 2" receiver. For fewer than 4 bikes, this pass through towing bike rack (with the pass through) works.
http://www.swagman.net/product/original3-towing/ . Of course, the same checklist for trade-offs applies.
As a final resort, my Suburban (which is now 11 years old) can support a hitch receiver on the FRONT of the truck so I could look at my bikes over the hood all the way to the Fort. That would help put some weight up front and help the tipping motion on the tow vehicle but it would just look weird. I've seen it but it's weird. So I'm not ready to go there yet.
I hope the Swagman or ProRac solution might work for you.
Bama Ed