Thanks for all the great suggestions!
I adore Manny's, have been going since I was in elementary school, but seeing as we're all coming from north and are likely to end our day no further south than Fullerton, I'm hesitant to have us all meet down there. And my concern with Frances' is that the suburban folks will be driving, and parking could be sticky.
I didn't consider M Henry because I only recall it in weekend mode, but now that you mention it we could probably get away with sitting for a while if it's mid-week. Plus, it's the middle ground, to be sure. Two are coming from Wilmette, I'm actually in Andersonville, and two are on Diversey.
Because only those coming from north have cars, Evanston and the botanic gardens might be a bit more of a hassle for three of us, but we could always take the Purple Line up and have those with a car pick us up... I like that idea a lot. Thanks!
So now I'm choosing between M Henry, Meinl, and Evanston/Botanic Gardens. I'll be sure to report back on what we decide and how it goes, since I know I can't be the only one who will ever need to do a business breakfast on the north side...