Heya's,
Coming out to me was a very hard thing to do. It was probably the thing I least looked forward to doing, lol. Heck, I never really thought I'd get to a point to where I would want to or could even think about coming out, myself.
By the time I came around to doing it publicly on facebook, I had been on hrt and part (most) time for quite awhile. All the people I saw or talked to regularly (including many at work tho I wasn't presenting there yet) already knew as well by then. It still took me a few months of thinking about it before I actually got the courage to do so, lol..
Me, personally, I'm a pretty private person until you get to me know me. I'm also extremely leery of posting things (pictures and private info) publicly like that too, on the web, cuz once its out there, its out there, you know? Outta your control then.
So, between me already being out to everyone who I saw and talked to regularly, basically the people who I am close to, and with how I am personally, the way I came out on facebook was quite simple and tailored to me. I changed my name to current one, my gender to female, uploaded like 50 photos that I been wanting to for a LONG time, and picked a new profile pic from that. (I also switched my sexuality since it kinda has changed, figured why not, might as well change that now as well). oh, I also removed or hid old photos of me.. I told a few friends too that I was doing so because I figured that it would help me, getting likes and loves and some positive comments about it. I then followed up on it by making a short post as well, basically saying something like this, " Hey, as many of you know by now, I've been making some changes in my life for quite awhile now. This is me now. I am open to talk about it and things so feel free to pm me if you have any questions, concerns, etc". That was basically it, lol.
I told a few people right after I did it (who knew and were supportive) and got positive replies from them. Many of the people who hadn't heard yet liked it too. Didn't get any negative replies back on either my post or in pm. Actually, I only recall one pm about it, from a half-sister who I almost never see or talk to, basically expressing concern over my safety since I just made things public.
I've since found out (a few times!) that many people didn't see it or hear about it or me... When they did find out they were kinda surprised, to say the last, haha.
Anyways, basically, how, when, to whom, and what you say and do depends on you and your situation I'd say. You're the best judge of that, go with what you think is best, you know? Do it how you feel most comfortable doing it.
If you ask me, I think I've done it pretty cautionary there on facebook. I didn't post a lot of personal, intimate details about it or myself on it like I've seen others do, I didn't mention I'm trans or anything nor do I anywhere on it, and I removed my old ugly photos so can't tell at a quick glance that I am. I did it that way on purpose, not out of shame or anything, but for safety and privacy. I have no issues talking about it but I don't need or want my personal info to be out there for anyone to see or do with as they please.
If you're trying to be cautious as well, doing something similar might work for you. A new facebook profile, as you mentioned, might be a good idea as well. However, as I mentioned above, its probably a good bet to say that not everyone will see your post and then won't know about you and your new profile.
Emotionally: I'd say, hope for the best, prepare for the worst. Many of the people who I didn't come out to are sound like yours are, as well, and I was really afraid to post anything because of that. I didn't really wanna check out facebook for awhile after I did it cuz didn't wanna see any negative posts nor did I wanna see my friends list # shrink (I looked at that before...lol). For me personally, I think telling a few supporting friends that I was doing it/ did it, helped me a lot mentally, just by knowing that there would be at least SOME positive comments there. It's hard to prepare for though cuz you can never know for sure what someone will say or think until you do it.
Anyways, hope this helps a bit at least. Good luck, let us know how it goes?