If the ride is in 6 months, with a proper training schedule they can do ti (all of them-- provided they stick to the schedule). Sticking to the schedule is the hard part because work and life get in the way of training However, 2-3 mid week rides and a long ride on the weekend that gradually gets longer and longer will do it. Will they have sag support (nutrition, mechanicals etc) or is it self-supported? 180 miles is a LOOONG way... The biggest problem I see is that you are in the middle of winter, when it is hard to train for anything outdoors unless the weather cooperates in a big way. Since you will be shepherding them around, are you going to do it as well? After all, you will have the training...and you probably have never gone that far in a day yourself

It is a worthy challenge, and the ones who complete it will have the satisfaction of having done a tough ride.

train safe-