I would highly recommend a Royal Caribbean Baltic cruise. We choose this cruise for its itinerary - Helsinki, Tallinn, Riga & esp St Petersburg & it was excellent! If timing permits, I would suggest the 12+ night Baltic cruise which might be a bit more relaxing than having to do excursions every day for 5 days straight to see all the ports of call.
Shore excursions: We were fortunate to have found Alla Tours for our day trips to St Petersburg & Riga. Alla Tours was excellent! - great tour guides, small tour groups & great value for money. We had the flexibility to see so many more things than a larger bus sized group would enjoy. Alla Tours took care of all the necessary documentation for St Petersburg. Visa not required.
We also did the Royal Caribbean excursion to Tallinn, but suggest that you would be better off walking into the lovely old town on your own.
Well laid out cabin. Compact, but roomier than expected.
Balcony was great, even though it was a bit cool to use it for any length of time while we were sailing.
Good closet space to hang clothes. Good sized bathroom with tub/shower.
There were 3 of us, including our adult daughter & the room was fine. Besides, we didn't spend that much time inside during the day anyways.