I, too, am a grandma and recently traveled to Belgium for three weeks.
I used a Patagonia MLC #48103 which was like Rick Steves' rucksack. I
carried a total of 22# and was very comfortable using it as a backpack
and not carrying it over one shoulder. It is very easy to put on my
back and even has a strap to attach it to your waist. The luggage
w/wheels is okay but what about using the wheels on cobblestones?
Wouldn't recommend tennis shoes. The only people I saw wearing them
were American tourists. I love my Ecco Walkers and have a pair I bought
specifically for travel. In addition, I carry a pair of Dr. Scholl's
inserts in my purse and about mid-day I put them inside my shoes and
it's as if my feet were walking on clouds....
Margo in Western North Carolina