I've been thinking about doing this trip over the past couple years at Christmas. My interest is primarily in the Devil's Elbow region and floating the Havasu National Wildlife Refuge. What has kept me from pursuing it is the driving distance from Colorado (you are probably closer), the vicinity of civilization (floating through the concreted Colorado River through Bullhead City/Laughlin is unappealing to me) and the inevitability of having to push through the sediment into Lake Havasu at the end.
If I were to do this section, I would probably put in below Needles and take out at Castle Rock Bay.
"There is NOTHING--absolute nothing--half so much worth doing as simply messing about in boats. Look here! If you've really nothing else on hand this morning, supposing we drop down the river together, and have a long day of it?" -Wind in the Willows