How do you (nonawkwardly) handle bringing a new boyfriend to an event with people who aren't even aware you've broken up with your old boyfriend?

A nonprofit organization with which I volunteer a good deal of my time holds two big-and-fancy fundraising events each year, one of which is Sunday. I’ve been volunteering with this group for two years and know its members relatively well. I brought my old boyfriend to the past three semi-annual events, and they’re all familiar with him as my boyfriend.

The last event was in July, when I was still with my old boyfriend, and since then, I’ve gotten together with the group for volunteering purposes independent of him, which was never unusual to begin with. Relationships never came up in conversation, so I simply didn’t have the opportunity to mention that I had broken up with him, let alone the fact that I was dating someone new.

On Sunday, I’ll be bringing my new boyfriend to the event. While I’m not shy about the situation at all, I’m afraid that people will feel awkward when saying hello to me and being introduced to him, unsure about whether this is a taboo subject of some sort.

Do I make light of it from the get-go? To each person I introduce him to, do I come right out and say something (in a jokey manner) like, “Oh, I broke up with X; meet my new boyfriend Y!” Do I simply introduce him as “my boyfriend Y” and expect people to awkwardly wonder what happened? I don’t want people to feel like there’s a proverbial elephant lurking in the room…

I’m also bringing him out to a rather large work-related function for the first time tomorrow night. About half of my coworkers know about my break-up and about this new boyfriend, while the other half of my coworkers have no idea Old Boyfriend is out of the picture. How do people deal with this sort of situation in general? I just don’t want people to think this is some awkward thing. I’ve been open about discussing my relationship status with coworkers when it’s come up in conversation, but it’s not like I ever made an announcement to the whole group about the breakup or the new relationship.

What’s the best way to handle introductions/stares/awkwardness at both of these events?