I'd say skip Golden and head straight to the arkansas river. Park n play at BV and salida holes till your arms fall off. Numbers, browns canyon, granite/pinecreek, royal gorge are all class III/IV river runs that will have good water and are fun down to very low levels (pine creek rapid is IV+/V-).
I'd skip the poudre. Its getting low, and the ark would be better. As for Golden, its fun at this level, and its great for denver metro boaters after work, but if you have some time to drive an extra 2 hours, the ark is the place to go for what you want. If you are absolutely set on golden, there are some good sections on clear creek above golden that offer III/IV boating, and the playpark is still fun. We hit it last night and had a great time. If you are staying in Denver and don't want to go as far as the ark, you could also check out Foxton on the north fork of the south platte which has good water from releases. Check all the sections out on www.eddyflower.com