I completely understand your concern. However, it is very atypical for a dog to need to wear sunglasses on a regular basis despite the strong sun. Also, the likelihood that they will tolerate wearing the glasses is not very likely.
So, simply avoiding prolonged sun exposure for several hours at a time, should be all that is necessary.
The trips to the other States. What else to ensure safety:
1. Ensure they are on a good flea, deworming, and heartworm preventative medicdation like the oral product called Trifexis.
2. In those other STates, ask the local veterinarians if there is any issues with infections like leptospirosis, canine influenza, or other infections that can be vaccinated against. Typically, most conservative veterinarans only do the core vaccines. However, if you travel to areas where a particular infection is more endemic, an extra vaccine could be worthwhile for extra protection.
3. If you are in environments where ticks are a concern, than choose a product that can help with kiling ticks quickly like NexGard flea and tick oral medication.
4. With travel history, I would also encourage getting a tick-borne disease blood test annually, as well as, a regular fecal test annually.
Hope that information helps. Good Luck