Maybe the clean break is the best way for you . . . if you're confident you can manage the fallout (shunning).
I would encourage you to consider carefully how you might word your letter. As an active JW you will feel naturally inclined to "play by the rules" . . . but all you need to convey is that you no longer wish to be known as one of Jehovah's Witnesses. You can make it clear (even though it won't happen) that you have no desire to stop associating with your current friends . . . nor to cease following the leadings and teachings of christ (not apostacising) . . . those are impositions THEY will place on you anyway . . . but you don't have to attach those labels to yourself . . . good luck.