Mark already mentioned some information which for example I had given earlier about Helsinki. I think through those links you can find many useful things. If you have any questions I'll do my best to help you. I know both Helsinki and Tallinn fairly well. If you stay in Finland only for about 4 days, I wouldn't recommend a trip to Lapland. It's simply a too short time and you wouldn't have time to see or do anything. You can fly from Helsinki to Rovaniemi (takes about 1 hour 20 minutes) or go by train (at least 10 hours). If you decide to go to Lapland, there are also many other more interesting places than Rovaniemi. Or is there a reason why just this town interests you? In Helsinki I can recommend Sokos Hotel Helsinki. It's very nice and situated right in the city centre very near to the main sights, shops and restaurants.

Tuija in Finland