@o&smom We are booked on the 11-night cruise that does an over night in St. Petersburg, so we get two days there. We plan to do a full day private tour to go see Catherine's Palace and the Hermitage and I'm not sure what else yet, but I thought using the "shopping" excursion on our second day would get us the church and some shopping! You sell that evening tour pretty well though! Thanks for the info.
You can do both, just like us on your second day. It will still be a much more relaxing day than your first. Enjoy!