Scandinavia Itinerary

I did a Scandinavian trip similar to yours a few years ago. I had 17 days on the ground. When I was planning, I quickly realized I couldn't fit Norway into the picture along with Denmark, Sweden, Finland, and Estonia.

You're trying to squeeze a whole lot more into less time. (It looks like about 13 days.)

So you are going to have to make some compromises somewhere. I'd strongly recommend you reconsider your aversion to flying mid-trip. I wouldn't cut out the trip from Copenhagen to Bergen, but I think it would be very sensible to fly from Bergen to Stockholm. This will give you much more time on the ground in the places you want to see, which is where you really want to be.

3 nights Copenhagen
Ferry to Oslo overnight
NiN to Bergen, 2 nights
Fly to Stockholm, 3 nights
Ferry to Tallinn overnight
1 night Tallinn
Ferry to Helsinki, 2 nights

This gives you a much needed extra night each in Copenhagen and Stockholm. If you don't want to stay a night in Tallinn, you can stick with your original plan to stay in Helsinki 3 nights and do Tallinn as a day trip. But the night in Tallinn amounts to a full day and a half, which it deserves. You arrive early morning, drop your luggage at a hotel, do plenty of sightseeing, and the next day you have time for even more in Tallinn before you catch a ferry to Helsinki.

If you are absolutely dead set against flying, I would save Norway for another trip so you can really immerse yourselves in the other places. Everywhere you have on your itinerary merits more time than you are allowing.

This is a very rushed trip, you are trying to see a lot in the time available. Too rushed for me, but maybe this pace works for you?

A way to get from Copenhagen to Bergen without flying and without going via Oslo is to take the train from Copenhagen to Hirtshals and then the overnight ferry to Bergen. I would also suggest the ferry from Stockholm to Tallinn and spend two nights in Tallinn.

Trip is too rushed, you aren't spending enough time in most of the places.

Badger and Lane have given you extra time with their suggestions.

I would ask if you have gone so far as to look at each city and see what you want to see there. That will help you focus on where and how you want to spend your valuable nights. In essence, right now you mostly have one full day in each city. Break that down to 2 sights (at most 3) in each place. Maybe in some cities, you have more and they are more important to you than places in other cities. It is good to know.

If your plan is just to arrive and walk around in city centers, there’s nothing wrong with that. It will just be a very fast-paced trip, getting a slight feel for each place to see where you might want to return. It sounds like this is not your first European trip, so that may be your style of a travel.