Welcome to RAGBRAI. Where in Colorado are you coming from? I have a small team of Colorado Road Pirates that do RAGBRAI every year. We’d love to ride with you sometime. Our training rides typically consist of 35-45 miles with a beer break in the middle somewhere. Gotta train those livers for this one. ;-) We are out of the Boulder Area (Erie/Ward) and ride North Boulder/Longmont/Lyons/Loveland frequently.
BTW – I agree with everyone above. Your plan is sound although it sounds pretty cramped. 12 people, 12 bikes, 12 sets of baggage/tents/gear might fill that trailer AND the van pretty quickly.