Easy to get on the MUP from Sibley... just bike north on Washington Street to Burleigh Avenue, where the trail starts. Two fun options, or you can combine into one ride with a little backtracking.
1. Ride the trail north, hitting Sertoma Park, Riverboat Park, Keelboat Park, and ending in Pioneer Park. A great option from the trail end at Pioneer is to cross River Road and get back on the trail and climb the hill... tough 1/2 mile climb but totally worth it for the view of the Missouri River from the bluff. Backtrack down the hill and retrace your route. The camels can be found along the Sertoma Park loop. Total round trip mileage is under 20 miles.
2. Ride across the river to Ft. Abraham Lincoln State Park. Both the Expressway Bridge and Memorial Highway Bridge have paved MUP paths. Round trip is about 25 miles. Great things to do at Ft. Lincoln... museum, Indian village, Custer Home tours.

Maps of Bismarck and Mandan trails can be found on the Bismarck Parks and Rec web site and the Mandan Parks site. For the Ft. Lincoln trail, check the TrailLink web site.