My plan is simple:

1. main light: 10w rated for 4 hours burn. 20w rated for 1 hr burn time. They both use the same battery, so will use Low [10w] until I need Hi [30w] and recharge the battery the night before.
2. backup: flashlight and bungee cords. Not great, but should get me thru
This ride should only be 90 min max. Hard to judge time as don't know how many idiots will be riding. A shower or two might keep the crowds down.

Don't know enough about your setup, but flashlights might work for you at well. Main problem will be length of time. If you were starting fresh, you could get some of those 24 hr mtb lights, but they cost a bit.