Just do laps on the day section, camp out at the put-in. outhouses are are right there. and less stuff to rig and de-rig, which = more time to sleep, drink beer, do another run... and all the rapids are on the day run. Overnight rafting is a serous investment in goodies. each thing is crucial, and you 'll want one of everything, so prepare for the reaming of your wallet.
and you want a topnotch poop containment device. it's worth it! bring a sun hat too though for the chama, cause theres a lot of float in between the rapids. where you might de-helmet. But if you DO wear a bike helmet, you could be ready to go for the Bike shuttle, which has been known to be a good option for that dead-end road on a quiet day. lol.
That being said, the wilderness section is spectacular, and should be done at least once or twice...:]
...and second what was said about an actual whitewater helmet....