Here's a round trip out of Denver. Hope this helps some.
Day 1 - From Denver, drive to Black Hills, 371 mi – 5 hours 48 mins. Stay in Custer or in Custer State Park at a lodge there.
Day 2 - Visit Mt Rushmore, Custer State Park, maybe Jewel or Wind Cave (we like Jewel better). Stay in Custer.
Day 3 - Drive from Custer SD to Deadwood SD, stay in Deadwood. 55.9 mi – 1 hour 24 mins
Day 4 - Drive to Devils Tower and then up to Little Big Horn. Stay in Billings. From Deadwood to Billings is 341 mi – 4 hours 46 mins
Day 5 - Drive to Big Timber: 82.9 mi – 1 hour 15 mins. Stay there.
Day 6 - Drive from Big Timber to Mammoth in YS: 94.4 mi – 1 hour 41 mins. Visit Mammoth, then drive down the west side of the park visiting Norris Geyser Basin, then to Old Faithful. Stay there or in West Yellowstone.
Day 7 - Explore the Geyser Basins around Old Faithful, drive to the Lake area or up to Canyon. Stay in Lake or Old Faithful.
Day 8 - Drive down to the Tetons, visit there for the day and stay in Teton Park or in Jackson.
Day 9 - Visit the Tetons, stay there again.
Day 10 - Drive back up to YS, stay in the Canyon area. Visit Hayden valley in the evening.
Day 11 - Drive north to Lamar Valley in the morning, then back to Canyon to visit that are before you leave.
Day 12 - Drive out the east entrance toward Cody, visit Buffalo Bill museum. Stay there or drive on to Thermopolis and enjoy the hot springs. From Lake Yellowstone to Thermopolis: 163 mi – 3 hours 16 mins
Day 13 - Drive back to Denver. 408 mi – 6 hours 10 mins
Day 14 - depart Denver