Are you planning to potentially evacuate with your chickens? I understand that may not be practical for any number of reasons, but evacuating with chickens could be as simple as having an extra rubbermaid container to put them in and making sure you have somewhere to go where you could have the chickens and perhaps having some extra hardware cloth to make a makeshift run once you get to where you are going.
If you aren't able to evacuate with them, the best thing you could do is to clear away vegetation from their coop in a 10-foot radius on all sides and leave them with a ton of extra water. I'm not sure it would save them if the fire really did roll through your property, but it's better than doing nothing.
Please stay safe! I know how scary wildfires can be.