Hey Sue,
I've never done the ride; no desire to either, but I did offer to support 2 friends who did it last year, so I can claim that I did DAMROD - drive around.....! The Redmond CC is adamant about PSVs...personal support vehicles and they're right to be as I spoke with some of the organizers beforehand. They have to work very closely with the park rangers etc and in the past some yahoos who were personal support for riders, rode too close and dangerously to riders, or stopped/parked their car in bike lanes or got in the way at official rest stops and the like so that is the reason for all of their warnings about psv's on the website.
I did go along and pre-planned where I would meet my riders, always at other spots than official rest stops (there aren't many of those tho) and I pulled completely off the road and out of the way...I had plenty of snacks and beverages for them...even cold water in a spray bottle, that I spritzed them with on the hot climbs...and stayed to do the same for tons of riders following them!
You'll do well to train for both mileage and climbing on this ride...the first 40 or so roll right on by and after you turn in Eatonville, the grade up begins to the park gate...then the climb up to Paradise, followed by a sweet downhill, before you climb a bit again up Backbone ridge...with another awesome downhill...the climb up Cayuse is in the heat of the day, after a century of riding, so all of my friends that have done the ride agree that that is the toughest part. There is of course a long downhill after you crest Cayuse down to the final rest stop at entrance to Crystal Mtn and after that there is about another 30 miles of riding to the finish. I let my friends enjoy the last miles on their own while I drove on ahead and got some ice cold brewskis for them to enjoy after they had their recovery drinks in the Enumclaw h.s. parking lot at the finish.
When I asked for their feedback about whether I was helpful or not, they stated that there was no way they could've done it w/o my help as there were not enough options for them to replenish their water supply, etc. to keep going...I kept 2 coolers in my car, filled with both ice water, accelerade, v-8, coke, juices and plenty of snacks...
All that being said, you've done plenty of long rides and mtn passes before so I'm sure you'll plan and train well to make sure it's a safe, fun ride for you to enjoy...
They're doing it again this year along with another friend and all have already asked if I'd consider helping again - see ya on the road!
Mary