Well, our party is at a library because that's where our playgroup is held in the winter, summer is at the park. However, we are in the basement, away from the main area.
Here's our agenda for this year: We are bringing various craft items, one mom is specifically bringing stuff for everyone to make Valentines for special people in their lives. Each child is also bringing Valentines for each child attending (around 20 at this point was the last count, I believe) whether homemade or storebought. Each child usuallly puts a small treat in each Valentine, whether homemade candy or a chocolate or a small silly toy type item.
We usually set up "stations" with the craft stuff. Sometimes people bring specific crafts for the children to make, but what usually works best and is most popular, are the boxes of "stuff", paper bits, lace, stickers, confetti, fabric bits, tissue paper, hole/shape punchers, glue sticks, glitter, and etc!

Each child is to bring a box or sturdy stand up type bag for their Valentines to be deposited in, we have decorated them before the party and at the party in previous years. Personally, I preferred decorating one at home beforehand because it was an additional cool thing to do and led to a smoother Valentine's exchange. I think that's what we are doing this year, so good

Anyway, we line them up along the floor and the kids deposit their Valentine's in them.
Okay, one family is bringing a boombox and any family can bring any music they want to be played relatively quietly (the library is upstairs, afterall, LOL!

). We have found the kids love to play musical chairs, all of them, up to age 13 or so

So, a couple rounds is on the agenda.
We are bringing a dish, several people are bringing sweet stuff, drinks, and a few are bringing a little more healthy stuff. We are bringing homemade hummus, tabbouleh, and pita bread. Just to even out a little of the sugar

This may sound like a lot, but really it's not, it's a very relaxed group. A very relaxed time.
You could think of silly games like Simon Says, always great in a group, LOL! I dunno, just thought I would give you and idea of what we are doing
