I agree with Kathy, we were on the same cruise as her and loved it.

What are they offering for Porto? One idea is to do a port wine tasting. That gets you to the south side of the river, across from the old city, with very scenic views.

If there is a free shuttle into town, I would also suggest just walking around the old town, and across the bridge to one of the port houses and do your own thing (if you are good at hoofing up and down). Porto is a beautiful place.

Honfleur is eminently walkable--we were docked a bit far out, but there was a shuttle bus available (although we walked it one way, so not too far.)