The printed topo book includes only roped climbs, so yeah, 27crags is probably the best database. The Ekenäs and Hanko area does not really have any rock at all (the rocks in the old ww2 tank trenches are not big enough to climb on), so you will have to move away a bit to find any decent boulders.
If you want to develop new areas, know that allemansrätten is the same in Finland as in Sweden, and I don't think anybody will care if you brush some moss of a boulder here or there. Of course, if you find a place with more potential, it is always best to first talk to the landowner. Main problems are usually with parking, so take care to not block tractors from reaching the fields etc. You can start your exploring of new potential areas on
https://www.karttapaikka.fi/karttapaikk ... asp?site=8.
Can't really commment on the kayaking, but the archipelago goes all the way along the coast.