To slick in Holland, I would suggest bringing the compact. I am assuming you have 50-34 in front, and the 29 in back will be plenty good. The steepest climb is around 6%, so you shouldn't have to worry about a low cadence. You may spin out on the downhill sections, but with 3500 of your closest friends in the ride, I would plan on being cautious going downhill.
I am also riding in the TBP this year. It will be my first time as well. Good luck, and maybe we will run into each other.