It sounds like it will be a fantastic trip!
I don't travel too much, but some of the things I find helpful are...
* Get enough rest BEFORE you go
* If you're having any problems with pain or walking, take advantage of the wheelchairs and/or motorized carts at the airport.
* Take advantage of the chance to board the airplane first, so you don't have to struggle with the crush of everyone at once
* Drink LOTS of water - yes, even if it means you have to get down the aisle mid-flight.
* Some people swear by the little cloth face masks - I haven't tried them so can't comment.
* Look online or at the library for a book on seated yoga stretches - that may help you get through the flight with less pain, as you'll learn how to stretch without elbowing anyone in any inconvenient spots.
As for the sun exposure - be VERY careful. Long sleeves - with sunscreen too. And of course, my most important tip (which you would have to expect from me....)
A hat (or several! ) with a brim at LEAST 4" all the way around.
When you're there - eat lots of wonderful fruit and pineapple.... (only peripherally a health thing - mainly an enjoyment thing!)
have fun, and we hope to hear a travellogue when you return!