Trouble Coming Out and I'm 28

Events and circumstances in my life had led me to the point where I am 28 years old and not publicly out as a gay man. I am out to three friends, but not to family members and other friends. From 18 to 25 I was in a relationship with a woman, which obviously had its fair share of problems. I'm lucky to have open-minded parents who I know would not have trouble accepting me, but I guess the idea of totally upsetting the apple cart scares me. I just feel like this would be such a surprise to them especially because of my past relationships. I can't imagine actually sitting down and discussing this face-to-face with my parents, so have considered writing a letter. I just need advice or stories from your experiences, especially if you were a late bloomer like I feel I am. I guess I'm getting to the point where I'm realizing this is a pull-the-band-aid-off-quickly situation, but it's still hard for me to pull the trigger.