For Quebec City, we stayed a few nights across the river in the town of Levis at Camping Transit last June. We were very happy with the very well-managed place.
They offer a free shuttle both ways to the nearby ferry terminal (or you can drive there and park), where you can board the frequent departures for a quick and very pleasant ride across the mighty St. Lawrence which arrives at the heart of the charming lower town of the old city. (Saves trying to navigate and park on the old, winding cobblestone streets.)
Great photo ops approaching the famous Chateau Frontenac hotel that dominates the waterfront. You can just spend hours walking all around the historic area, then take the funicular car to the upper town and do more. Lots of nice shops and restaurants, very visitor-friendly but without any overly tacky tourist junk.
It's quite a lovely place to visit and we will return.