As most people said,
1. try to buy upgraded seats for more legroom.
2. Stay hydrated. I brought along little electrolyte powder packages (think Pedialyte) to add to water whilst flying.
Amazon’s brand is pretty good. The individual packets can be poured into a bottle of water. Not at all messy.
3. Walk around or move your legs while seated. A lot of setback entertainment feature exercise options to do while seated.
4.Take baby aspirin and talk to his doctor about possibly starting an aspirin regimen ahead of time.
5. Wear compression socks.
6. Don’t try to see it all; pacing is important. 7. Get insurance regardless of the cost. Medicare is useless overseas.
7. If you can, give yourselves a jet lag day upon arrival so you can start to get better acclimated. Take small jaunts close to your lodging that day. Don’t nap!! Force yourselves to stay awake that first day so you have a fair chance of sleeping that night.
8. Enjoy making memories.
BTW,Pickpockets are a thing. Go to some blogs or YouTube videos to learn some low cost effective hedges against it.
I traveled last October at 69. I’m going again this year. I was on blood thinners for a blood clot in my lung. My doctor merely stressed some of the suggestions above and told me to be very, very faithful about taking my pills on time. I’ll be talking to my doc about whether I need to go back on blood thinners and whatever else she’d recommend.