Do I attend a celebration service for someone if I was not formally invited?

My friends stepfather recently ped away and instead of having a traditional funeral they are having a gathering at a yacht club to celebrate his life. She keeps talking about the event and said she was sending out invitations (of which I never received). Do I just take it upon myself to show up? I feel a bit awkward, it is not a traditional funeral and I was not officially invited. But she is a friend of mine. Any opinions?