We've evacuated for wildfires twice in the twelve years we've lived in this house (the Cedar Fire in 2003, which burned right to our back fence, and the Witch Creek Fire in 2007, which ultimately didn't come very close to us). Because of all the animals (we were running a boarding stable at the time, and in 2003 we still had a *lot* of reptiles) there was never much time to pack anything else. Negatives, an external drive with most of our important stuff backed up, legal documents, and a couple of instruments. But at the end of the day the only really indispensable things are lives.
Good luck and be careful. They do not make events much more scary than a big wildfire.