I agree there is no right or wrong answer for this. Everyone expresses their emotions differently. My mother recently passed and my father has not shed a single tear; but, I know he is lost without her - it shows in many other ways. I, on the other hand, have had many good cries - in Safeway, on public transit, in restaurants, etc.
As to the friends or relatives part of your question. I think there may be friends who were closer to the deceased than some family members. That's OK! I have had friends I consider family; and, I have family members that I am not that close to.
Grief is such a personal thing.