Try the local boating stores for pools during the winter: Mountain Miser, Confluence Kayaks, Aplineglow, Boulder Outdoor Center, should be others as well.
As for winter boating: Gore was running recently (IV-V), Shoshone runs almost year round (glenwood springs, 2.5hrs from denver west on I-70, play run), maybe bailey (IV-V) or waterton(III) (Deckers, South of Denver in the mountains)-ask for front range boaters for that info.
Lucky 7 is running, its a 3-4ft recurling wave at the base of an overflow dam near Grand Junction. Its a long drive for just that though, more like a weekend trip skiing and kayaking would be better. Westwater might also be going, but requires a permit from blm and its just over state line in Utah. 17miles, 5miles whitewater, lots of flat.
Hope that helps