Upvote:3
Since you already have your visa, there is no point in changing it. You would only do so if the was a substantial, material change to the circumstances of your visit.
In this case, your situation is such that your travel itinerary has changed, even though you are still primarily traveling to Finland. You do not need to notify the embassy or ask for a visa change.
Croatia offers visa exemption for Schengen holders under these conditions:
From the information you have provided, you meet all the criterion, so enjoy your stay.