if you aren't into WW, a classic run is thru Ruby and Horsethief canyon - Grand Junction area, about 250 miles from Denver. Google for BLM Ruby Horsethief to get current info - requires reserving campsites - should be able to get something weekdays I'd think - stay at Black Rocks (about 8 sites there) or Mee Corner if you can
this is generally flatwater to CI paddling - biggest issues at lower water levels are not getting hung up on the gravel bars - a CII bit of rapid can set up at entrance to Black Rocks
The Gunnison, from Delta down to Whiteater, or continue on to junction with Colorado and take out at Fruita is also a nice run - one CII rapid, rest is easy. Nice hike up Dominguez Canyon (and camping there)to see lots of petroglyphs
NOTE! All of these trips require a self-contained toilet and fire pan along (check for current fire bans) - can be rented
for both of those trips, Rimrock Outfitters in Grand Junction can supply/rent the toilet - they'll clean; and provide shuttle service.
Touring Kayak Paddles