People tend to be rather family- and home-centric during the core Christmas time. However, that time has shrunken from noon 24th to 25th early afternoon. Nevertheless, things have changed over the years, and there are also restaurants that stay open through all Christmas time, so no problem with that. Takes a bit googling or walking to discover which ones. One Christmas special I warmly recommend, is to go walking in Hietaniemi cemetery during the evening of the 24th. People lit candles to their beloved ones’ graves during Christmas (another family-centric tradition) and by the night of 24th this large cemetery turns into a big field on candles. Very beautiful! And there will be other people too, who come to enjoy the atmosphere. It is not a long walk from Kamppi metro station. Another nice tradition easy to participate is to go to public sauna on the 24th. Be warned though: they will be packed. Have fun in Helsinki. Check also Helsinki’s pages more close to Christmas, if they add some info on open restaurants. https://www.myhelsinki.fi/en/see-and-do/events/christmas-in-helsinki

This hopefully helps as well:
https://www.myhelsinki.fi/en/your-local-guide-to-christmas

Also, just as a side note, staying near Kamppi metro station means that you staying in the very center of Helsinki. Which is good. :-)

Not so problematic than in Dublin last time I was there after Christmas :) I'd rather say that many places are open. Central Helsinki is quite easy to walk through and you'll soon find your bearings. On Christmas eve public transport and many restaurants quite down though. But from 26th on things are pretty much normal.

Hello Marsha.
Many restourants will be closed during the seson.
https://www.tableonline.fi is easy to use for finding restourants that are open and have avaliability. I recomend to reserve in advance. For drinks it is easyer, most bars will be open as normal.