Baltic cruise; Copenhagen, Warnemunde, Tallinn, Helsinki, St. Petersburg, Stockholm.
Do NOT get a Sky Suite; it's not necessary. You get a butler (who serves two snacks in the day) and larger cabin & bathroom, but not worth any significant price increase...just get a normal balcony-grade cabin and you'll be fine. Never get a cabin with a window (only) on any ship...not worth the price increase and you get extremely limited "view." Only get either an inside cabin or balcony-grade cabin on any ship.
Weather in Baltic ports (July) is very fickle; take umbrella, shorts, light-jacket, cap. All Europe cities are NOT ADA-compliant...if you have walking difficulty (stairs, cobble-stones, etc.), then you will not be able to go to all sites in any city. I cannot stress this enough, there is significant walking with no accommodation at all sites that is not for the challenged.