{the following is stated from my perspective as a pastor--take it for what you will from there}

Funerals are for the family and friends to have some form of closure by remembering/honoring/celebrating a person's life and to proclaim the hope of resurrection in the midst of a physical death/loss (if people of faith). It is also a time to show support for the family/friends by your presence, even if not by words. If you feel your presence would be such a support, then go. Otherwise, I'd say its ok to skip it. I also second the "main" funeral attendance only as well.