How can I tell my girlfriend (when I meet her) about my belly button fetish?

I'm not going to tell her right away but sometime after we start dating I was going to. I want to be able to tickle, kiss, and blow raspberries on her belly button. I also want to come up from behind and tickle her sides and belly. I would be open to whatever fetishes she has and I would want her to keep my fetish a secret just like I would keep hers a secret.