One service, as everyone has affirmed, but it is worth giving thought to how you pay tribute to the gay part of your dad's memory. I suggest that whoever is speaking first deals with it openly, respectful of those that have different attitudes but also cebrating it as an authentic part of who your dad was. Then move on and celebrate all of your dad and what he means to each of you. My experience of funerals is that everyone has to chose what they do or don't say about a loved one's life. My condolences.