Do we need a visa to do this tour if we are arriving on a cruise ship
Look for a YouTube channel called The Wayaway, they have done a video recently covering this when they visited. Its a great tour but wear good shoes as you cover a lot of ground!
My understanding is that cruise ship passengers that just stay for a couple of days do not need a visa, but need to be accompanied by a licensed guide and sleep on the ship.
I'd check with Peter from Peterswalk to see if they can serve you.
Get an answer from Small-Group Walking Tour of St. Petersburg staff and past guests.