As someone who lives in a high risk wildfire area (we literally get about 3-4 wildfires a year), my advice to you is to get your own horse trailer or at the very least set up a plan with at least two different people (in case one is out of town during an evacuation) who are responsible and have trailers large enough to accommodate your horses and their horses. You would also need to make plans for various locations to take your animals that are far enough away from fire danger zones, as well as water, hay/feed, and any other supplies you may need. That is the safest option for your horses.
Riding them across a steam/river/etc. (even a wide one) is not a valid safety option as fire can easily jump breaks like that with wind, etc. Plus smoke is still a hazard in and of itself and can have long term consequences.
Setting them loose is really your only option at this point if a fire were to break out tomorrow. Don't rely on just spray painting your phone number on them because it can be smeared in the chaos, especially if they get caught up in any water or slurry drops. The new ICE clips for manes are really nice and are probably a safer way of keeping your information on your horses should you have to turn them loose. Most wildfires here you are only given a short (and I mean SHORT) period of time to evacuate before road closures are put into place and it becomes much more difficult to get in/out without escort. Rescue workers also generally are not able to assist any animals, although many try if they can safely do it. Firefighters also prioritize houses and farms that have a safety space around their homes/barns/etc. (at least in our area) which means clear any brush, dry matter, or other fire hazards from around your property and you will have a better chance of them working around your house should they be in the area.
I know you said your community doesn't really have any large animal evacuation procedures in place, but this may be an opportune time to bring up that concern at a community meeting and perhaps a plan can be put into place that gives locals with large animals and livestock a safe location to transport and keep their animals while evacuation orders are in place. Water, feed, and bedding donations also need to be considered in this case.
I also make sure to keep copies of important paperwork for all of my animals as well, including vaccinations, Bills of Sale, registration papers, Coggins, identifying pictures, etc. Occasionally your animals must be kept at facilities where you are not able to stay and in the chaos there can be a lot of mixups so it is always good to have as much information on your animals as possible (horses or otherwise).