compo I don't think it's comparable to ice cream flavours, really. I knew I was straight before I was ever sexual with a man, and I think it's commonly accepted that most people who are gay know their orientation in childhood / puberty as well. Did you really not know what your sexual orientation was until you'd tried out every possible combination?
adrenalinejunkie if I understand you, your unease comes from feeling that even those closest to you are completely oblivious of a big aspect of who you are (i.e., your sexual orientation), not of something you'd like to do. They're two different things, and if I felt there was an aspect of my basic personality that DH didn't "get", I would want to share it with him too.
I agree, though, that you need to be careful how you do it. If you treat it like a big deal, your DH could be forgiven for being worried about it or for feeling some level of personal hurt. He might think you're getting at something else: that he's not enough for you, that you want to explore that aspect of your sexuality, or that you haven't felt able to trust him with the whole truth of who you are.
Maybe one way to broach it, if you feel you need to, is within the context of the "slightly homophobic" attitude of some family members. You could confide in your DH that you find their comments hurtful and offensive, in part because you have felt yourself to be bisexual for most of your life. You could say that your bisexuality is neither here nor there because you love him and are committed to your marriage (assuming all of this is true, as you've said that it is), but that homophobia is still hurtful to you because bisexuality is an aspect of who you are.
I just think from your DH's point of view, because you've kept it from him in the past, he's bound to think "why is she telling me this now ?". If you provide the answer to that question (because you're bothered by some family members' attitudes and need his support and understanding), he may be less likely to jump to more worrying conclusions about your motive for telling him.
Good luck to you.