First off, I really don't think anyone will notice. I've kept mine hewn for most of the past 30 years, mostly because I wore tights/pantyhose on stage, and they looked horrible on hairy legs, and I think MAYBE one or two people in all that time have even said a word about it, and if they did, it was just in passing and nothing more was said of it. I'd say you really have two choices: either tell anyone that asks (and I doubt anyone will) that you just don't like the looks of it anymore. My uncle had hairless legs and I'm pretty sure he shaved `em, because he was pretty hairy on his chest! He wasn't at ALL trans in ANY way. Secondly, shave `em now, but continue to wear longer pants for a while longer, a week or two, then start wearing shorts. Chances are, anyone that's seen you in longer pants all this time will not recall that you had hairy knees and when you whip `em out in a week or two with no hair, nothing will be noticed.
As for me, I just went ahead and shaved `em one day when we were about to play a gig and nobody noticed or said a word about it! The more you point it out, the more people will notice, so, just forget that you shaved `em and act completely normal.