CU has a kayak club but their amount of activity oscillates over time and I think they may be in a trough right now as I never see them out and about. Regardless, you should probably join and take advantage of free gear, gas, vans, and such.
Your information is more or less correct, but in reality the bulk of the runoff really only occurs for about a month, usually in June. During the month there are lots of great runs near Boulder, almost every creek/river that comes down off the Front Range has some good stuff, but it's over quickly. There are a few dam controlled runs within semi-reasonable driving distance that can last into Oct or even early Nov.