Allison wasn't there, because she spent the night hanging with Lydia in the hospital.
Bonnie is dead :(
Faith isn't 100% but she would have stopped by and said hey to Jim and Regina and stuff. Ate some free food and all that jazz.
Robin was obviously there, since he's been staying there with Regina & co. He would have mostly stuck close to Regina and the kids, but tried to be friendly to others, too.
Rose was clearly there. She spent most of her time with Jim, but also played with the kids and traded off hostess duties with Regina, making sure everyone had food and drink and stuff. The fireworks were ALL REGINA, though.
Skye was there briefly with Ward, I think, since he commented on the initial post about stopping by after the town memorial. She was pretty quiet, but tried to be friendly.
Snow would have come by to support Regina, mostly, and check on how she was doing, even though she's not really doing well.
Stefan would have gone if dragged, so Maxi LMK if Caroline tried to drag him along!
Thea would have been there with Ben and his mom, I think!