Will your group be supprted by a vehicle, or will you be
carrying all your own equipment? Cyclists can average more
miles a day if they have vehicle support. Ft. Mandan to Ft.
Peck is approximately 390 miles. If you do 60 miles/day you'll
finish that in 7 days. But you'll have to plan your overnights
where there are services, so some days may have more
mileage, and some days may be less.
Yes, 4-5 days would be average to travel the Lolo Motorway.
It will be much easier with vehicle support, but the riding will
still be difficult. It's quite a climb up to the ridgetop, and then
there's a series short, sometimes steep climbs and descents.
But it's beautiful, and you can see what the Corps of
Discovery saw (hopefully without the snow, of course!). There
are only 2 designated campgrounds along the route, very
near each other, but there are many spots for informal
camping. Most of them are used for horse packing or hunting
camps, and are located near running streams. Remember to
bring water filters with you.