One week in Finland in Sept/ Oct this year.

To be perfectly honest, I think you need to go back to the drawing board and try to figure out what it really is that you want to see and do.

It's not impossible to see the northern lights in September, but the probability is very low. I'm also going to link to this old thread I wrote on the subject: https://community.ricksteves.com/travel-forum/general-europe/how-to-see-the-northern-lights-a-short-guide

I don't think there are any ice breaker cruises in September. It would be a bit pointless to offer them since there is no ice on in the bay then. For ice breaker cruises the spring is better, here is a map of the current ice conditions: https://cdn.fmi.fi/marine-observations/products/ice-charts/latest-full-color-ice-chart.pdf As you can see there is still a lot of ice.

When you mention igloo hotel, do you mean those small cabins with large windows or an ice hotel?

I think some of the Santa theme parks are open all year though.

Thanks for useful reply. After going through the link and your post, I am also inclined to postpone it to next year March/April. Icebreaker cruise is something I just came across somewhere and mentioned without thinking..Let me plan it out again and get back.

Good idea. March/April is a lot better for icebreaker cruises if that is important. There are two major icebreakers that offer cruises in the Bothnian gulf, one is based in Piteå and one Kalix. There are connecting buses to several towns, in both Sweden and Finland.

March/April is not that great for the northern lights though. There will still be dark nights, but the sun sets later and rises earlier.

Thanks a lot. Will comeback after replanning.