I've always wanted to try a swap meet! Looks like a lot of fun, maybe I'll try to organize one by myself :D
Go for it! It's not much different to any regular meet, especially if you get everyone to share a list of the things they have for trade before the meetup, so they can plan trades. That way everyone isn't carrying suitcases full of stuff that they're not sure if anyone wants. We did that, then just brought a bag each of smaller items for impulse-trading.