If handguns, I would buy the VCI paper, and once wrapped, put in a small dessicant pack and VACUUM SEAL. You aren't going to trap enough moisture as there is practically zero air in the bag. Then place in your box. Further protection, place in a plastic gun box. If box is underwater, the vacuum bag will protect the handgun.
I DO like the idea of a wooden crate also.
BTW, Check with a few of the gunstores, they would most probably take a crate of whatever size you needed and store for a reasonable price. And pick one 10 miles inland that has been operational for a decade..... Get some insurance on them. Take plenty of pictures and if you do a crate, screw it shut and tape the seams well with a good duct tape.
Or rent a small storage building, again, inland, and put that crate in it. BTW, being in FL, I'd probably put that crate on a 2x4 stand that is as high as you can get it inside the storage building. If building survives and a 2 ft surge, you want it 3 ft off the ground. Just say'n. And prepay for your length of tour plus a couple of months. (You might not get back to FL directly) OH, you might find a storage building with interior humidity controls, that would be worth it if you have long guns. BTW, cheap vacuum food sealer is cheap....