If they are your friends, they won't tell anyone... But you should be completely comfortable about getting out of the closet.
Tell who you want and ask them not to anyone else. If you can't trust someone than they really aren't your friend.
No guarantees when telling secrets that they will be kept secret. That is the risk you take for telling someone something in confidence .. The more that know, the higher the risk of 'it' getting out.
Just be yourself. Everything doesn't need to be published.