Are open-toed sandals acceptable for daytime in Paris and London? We will be traveling in June. Thank you.
Yes. Wear them & enjoy!
I have worn sandals in both cities and I was not the only one!
I think two shoes is best.
One pair would be sandals that can be worn with a dress to dinner or with a swimsuit to a pool or beach. The second pair should be a heavier pair of walking shoes for any major walking/hiking or bad weather.
Wear the heavier pair on the plane and pack your light ones. When you are in your lodging wear whichever shoe feels most comfortable for the day's activities.
Even in Italy where you aren't supposed to show shoulders or knees in cathedrals, your toes are still okay.