Be sure to pack on extra week of medications as a safety measure. Also, put your medications in your carry-on.
Wear the most comfortable things you can...including shoes. Drink lots of water before and during the flights. This can help you from getting sick.
Some people carry neck pillows. I have never needed that but that's another idea.
Be sure to get up and stand during the flight. If that means you have to get in line for the bathroom, that's great. This helps with your circulation. I'm glad you are taking the stretching exercises with you, too. These were designed for flights.
Pack a little snack of some kind on your carry-on. They don't serve much, if anything on flights these days. If you are stuck on the turmac, you will be mighty glad you have a snack and, of course, a large bottle of water.
Most importantly, have a wonderful trip!
Sherrine