I was in your shoes about two years ago. I had run across some skeptical podcasts, and had been listening and thinking a lot. I spent some time talking to my husband about things and he took that "well, that's all very interesting" stance to see where this was all going. I remember one night being in the car with my husband and in a rush of panic saying to him "I think that maybe everything I've ever believed is wrong." I was pretty freaked out. I was quiet about all of this for about a year. I talked to people on forums, read blogs and thought a lot. I was really afraid because I had always been told that 'losing my faith' was a bad thing. It took me awhile to accept that thinking for myself and coming to an alternate conclusion was not actually losing anything.
As far as letting people around me know, it was a slow process. I didn't use the word 'athiest' for two years. I am now comfortable enough to identify as an athiest. But I also realize that the fact that I don't personally believe in god doesn't mean that it is impossible for god to exist. I also realize that I have no right to try to convert anyone, any more than religious people have a right to convert me. When my friends and family realized that I believe what I do, I am comfortable belieiving as I do, and I am not going to try to attach their beliefs, all was well.
Questioning your beliefs is not an all or nothing venture. There is nothing wrong with doubting. There is nothing wrong with questioning. And taking the position of "I don't know" will not be threatening to anyone around you. If those who are close to you try to convince you that you are wrong to doubt, just thank them for their concern and keep thinking. As long as you don't attack their postion, they will probably accept yours - whatever that turns out to be.
There are no right or wrong answers. And not knowing is not bad or wrong. The truth is that no-one really knows anything for sure. So keep asking questions.