most tactful way to announce our engagement?

[Lydia]

Unless you are 12 please do not announce your engagment via Face Book. After you announce it to your friends and family you could mention it there but not before. Using FB for something so special seems a bit tacky.Sending engagement announcements has really fallen by the wayside as far as I know.That formality is not really practiced much any more. If you have older relatives who would be use to things like that I would send out personal greeting cards telling them about your engagement and then put an announcement in your hometown newspaper for friends. You will be inviting the people you want to attend by sending them a wedding invitation so do not send out wedding announcements after the fact unless you are fishing for gifts. Once people see that you are engaed they will assume you followed through and got married so no need to send them something telling them you did.
Congradulations to you !