Depending on how great you want your audio to be and how much expsense and trouble you're willing to go to, you could have a soundman with a shotgun on a boom pole - but if the speaking can be interrupted by others, he wouldn't be able to catch everything as well as you'd like.
You could put a lav mic on everyone, but what a job in post!
If your table is small enough, you might rig your lav in the center. Be sure that whatever is beneath it is not a hard, smooth surface and that it is isolated from sounds made by coffee cups hitting the table, etc.
Boundary mics are made for things like this. You probably should look into those.