I spent 7 days in Hel a couple months ago. Did lots of the things listed here, but also one not covered - a day trip to Fiskars. You can do it either via a train/bus combo or all bus. I picked the combo as I like trains.

Fiskars is the home of those orange handled scissors we all have somewhere in the house. They don't actually make them there any more, but the town has done a wonderful job on preserving the history. Very sweet, charming, interesting place.