The companies mentioned are all excellent suggestions ones so far.
If you're on the west slope of CO, Adventure Bound is a great company as well. They do the Yampa, Green and Colorado and have been doing that since the 60's. They have some old-school boaters in their crowd passing on the knowledge with great tradition.
As for this season, you should go with the outfitters that meet your travel plans in terms of location, but stay with those that have a good history of doing business and perhaps choose their most 'mellow' trip.
Why? There have been three river deaths this last week already, two rafting and one jumping into a river without a life jacket. BE AWARE that you are coming out here near the river's peak (where the rule of thumb is that they peak near Memorial Day Weekend) which means HUGE water. Having newbie guides show you a good time will compromise your safety.
Don't mean to scare you, but besides the peak of the season, CO is also having an above-average waterflow as compared to the last six years, and not many boaters are still versed at these levels and need to proceed with caution.
Please choose wisely and maybe take the easiest 'float trip' you can find. That way you are sure to avoid the adrenaline class III-V hotspots.
Groove on with joy and love all.