Ibuprofen. 600 mg starting first thing Saturday, then every 6 hours for the rest of the trip.
Bicycle shorts under your stuff. The extra padding and compression helps a TON.
Move around as much as you can. I know your options are limited but even little movements help a ton. Move foward and back on the seat, move your feet...heels on the pegs..toes. Do it often, every 15 minutes or so. Also stand up on your pegs if you can.......
We won't be going that fast on the freeway Saturday. That stretch of 81 is HIGH enforcement. I will be surprised if you can't keep up with me on 2 lane, I am fast but that bike of yours will move along real well. Dan was able to keep up with me with his China bike and that is a 250. I had him on the straights but he could carry way more speed in the corners.