Your skill level and trail experience will have more to do with your success/fun than how well your rig is set-up. If you aren't currently successfully running trails where 35's are the norm, and doing it with little drama, i.e. no issue figuring out how to get your rig through a tough situation, or quickly figuring out how to get your stuck rig unstuck, the Round-up may not be the best time to try and run the Rubicon. With your rigs current set-up it is going to be a lot of work for you to get from Loon to the Springs, and out to Tahoe, enough work that you wont have anytime to enjoy the surroundings, you might not even make the Springs in time for the BBQ.
If you don't have the trail experience, I would recommend trying to find someone with an empty seat and run the trail as a passenger, preferably in a rig running 35's/37's, it would give you an idea of the difficulty of the trail w/o trying to run it with all the rigs in the MCR, as well as the normal amount of traffic the Rubicon has on the weekend.
If you do decide to run the trail with your rig, rocker protection is a must, and I would have to agree with the recommendations for dual cases or lower geared single case. IMO, being able to creep up onto/off of ledges and rocks is far more useful than a locker, you can always stack rocks to gain traction, on the other hand you can't do much to slow your approach/departure, and in my experience speed is what usually leads to broken parts. I would also give yourself more time to get home, i.e. maybe plan on leaving for WA on Monday/Tuesday instead of Sunday, nothing worse than being under time pressure to get home as well as just trying to get back to pavement. One time it took us over 8 hours to get to Tahoe from the Springs, we left at noon and caught up to those who left 3-4 hours earlier just a little ways down the trail.
If you don't already have the 1/4" material lying around/getting it for free, 1/4" tube is overkill for sliders, pretty much anything in the wheeling hobby, too much extra weight, save your money and go with .120(1/8"), it is plenty strong enough with a proper design.