It went really well. We had about 20-25 people show up, or double the number I expected from the RSVPs, and they brought a pretty good variety of side dishes, pop, and sweet stuff. Couple of folks had trouble with the heat, probably on account of drinking too much pop and not enough water in the 90-degree heat; staying in the shade doesn't always help. By and large the invitation and coordination processes went well, so the only thing I'd change would be the meat selection. Ribs don't work well on a regular grill, and not all of what I grilled wound up being eaten, whereas the burgers and brats all went and fairly quickly at that. Everyone did a fair amount of mixing and talking, which I was glad to see because I'm worried about possible cliquishness in the staff.
So I'm chalking this up as a success. We'll have to do another one of these, preferably when it's not so damn hot outside.