I don't know how long, or if I can.
I know a way to convince them you are happy, but I think you probably already thought of it, even though you haven't invoked it in your post. It's an archetypal way to make people at ease. After that they will accept how you are, when you'll not seem so happy. The way is to make jokes. I don't say you need to be a clown. But making them laugh a couple of times, tremendously improves the atmosphere. Then they will accept your quirks, I think.