Northern Europe Travel

We are experienced world travelers, having lived and worked internationally. We have done a lot of independent travel around Europe using train travel, and Asia as well having taken a 14 days cruise in October 2015 through the Adriatic, Ionian, and Aegean seas. We are now seeking feedback from other world travelers on the following potential itinerary: Start travel early September 2017 for 17-21 days in Northern Europe, specifically flying into Amsterdam, visit for 2-3 days; travel to Berlin for 2-3 days; then onto Warsaw for 2-3 days; then travel through the Baltic sates staying 1-2 days in each state; then onto St. Petersburg for 3-4 days; then to Helsinki for 1-2 days; then back to Amsterdam for our flight home. A lot of walking would be a problem for my wife. We probably would require folks in each place who have the expertise and knowledge, have good language skills (Both in English and their Native language) could drive us around to points of interest each day we need a car and driver, and share about themselves, their country, city, locale. *Are the number of days enough in each location to enjoy specific locales, culture, food and people? *Any and all suggestions welcome as to who might best be able to work with plus give us an idea of cost not including airfare from the U.S. to Europe? *Would a cruise be more appropriate for parts of the trip and then set-up mini tours with local guides? *Perhaps using a ferry from Helsinki to St. Petersburg and back? What about visa requirements for Russia? We understand that if on Holland America for example we do not need a visa as long as we take their local tours. *What else should we know about planning this trip? Thanks for your help and input.