Sounds like a ton of fun!
I tow with a 4Runner, too. Before that much travel in one go, I'd suggest you review and tweak your towing setup to make it as efficient as possible. The satisfaction and relaxation gained from a well-tuned setup is reliable and invaluable.
Newer, properly rated and inflated tires, service/lube axles/bearings, inspect/service trailer brakes, review your wdh setup with your trailer fully loaded (as you will be traveling), review your 4Runner's tires, brakes, exhaust, etc.
This can help prevent trip interruptions and unexpected breakdowns in unfamiliar areas. You'll never regret preventive maintenance :)
You may wish to clean and run the trailer's furnace a bit with all the doors, windows, and fans open and running- especially if your voices are sensitive to the dust that collects in these systems over time.
You may not need the furnace, but if you're surprised by cold, you surely don't want to have any problems.
Good luck and have fun!
