We have a long flight to Sicily coming up in a couple of months and thinking of upgrading GOING because after a 2 hour ride to Boston airport with the Two hour wait and after that long flight we have a 6 hour layover in Munich before a 2 1/2 flight to Catania. Then a one hour ride to the hotel!If I were only going to upgrade one leg, it's the return, because facing that flight at the end of a trip can be a drag. Of course, there's benefit to arriving refreshed as well, so it's a toss up sometimes.
But in your case, picture yourself on the last few days of your trip, after flying business, knowing you have the return coming up, and it's coach.
That person will be glad you upgraded, if they are anything like me.
All these decisions are case by case, but that's what I'd do, except I'd have left the kids in coach both ways - yours are old enough.
I saw on line the upgrade to Premium Economy from Coach is $400 each. We have refundable fare and not sure if upgrading it would still refundable. Currently we have aisle seats across from each other - wheelchair ( for me) tickets.
I am 68 with the bad back and my husband is 70.
Business class, however is way too expensive for us. Can’t justify it.