I presume you're kayaking with a group of novices. The Upper Colorado's likely to be pretty chilly but from Grizzly Creek to Glenwood Springs will be a nice float and lots warmer. You'll have the bonus of a riverside hot spring on river L near the end of the trip. Should be a good paddle for any novices. The river's wide enough any beginners should be able to avoid the more challenging parts of the Class II rapids there.
The hot spring is pretty sulfurous, so here's the tip for everyone - bring a gallon jug in their boat, then fill with river water before soaking and put the jug in the hot spring. By the time you get out, you can wash the sulfur smell off with the now-warm (but not stinky) river water.
Leave a thermos of hot drinks (or several) in the car at the takeout too...
Have a great trip!
Nothing in the world is more yielding and gentle than water. Yet it has no equal for conquering the resistant and tough. The flexible can overcome the unbending; the soft can overcome the hard. - Lao Tse