I suggest that before you make any flight plans to Scandinavia, you first research in detail, your transportation within the area. From your post, you would like to cover a lot of ground in two weeks and would spend a lot of time on the road between destinations.
Several years ago, we went through this exercise, mapping driving routes using the ViaMichelin web site and checking on public transportation schedules. If driving, the distances between the major cities is great with not a lot in between to see, other than the fabulous scenery. You also have a potential problem with auto dropoff charges. We also looked at a Baltic cruise, but except for stops in the major cities, you get very little exposure to the countryside. We concluded that our best option was to take a land tour. Friends had taken The Scandinavian tour offered by Globus and recommended it highly.
That Globus tour begins in Copenhaven, so you see parts of Denmark, but does not include Helsinki or Tallin. You do spend a lot of time on the motor coach between stops, but that is more enjoyable than if you were to drive. The scenery in Norway is breathtaking and we were taken into areas that we would not have experienced had we driven. It also includes sailing through fjords.
Several years later, we took the Grand Circle river cruise from Moscow to St. Petersburg, with their extension to Tallin and Helsinki. We feel that we have covered the Baltic area quite well, given the constraints of time and funding. Whatever you end up doing, do not miss Tallin, either on this trip or another. Prior to our trip, I would not have considered Tallin as an end destination, but certainly would consider it now. The ferry between Helsinki and Tallin was very convenient and we have friends who have taken it both ways on our recommendation.
Scandinavia is a wonderful, interestiing and scenic area to visit. You will enjoy your trip, but do plan your transportation carefully.