In-laws in town, need great atmosphere + food?
How about Periyali
Eleven Madison or Gramercy Tavern? I had brunch at Eleven Madison where my parents met my future MIL for the first time and I couldn't have asked for a better place.
My future hubby and I also took my parents to Gramercy Tavern when they visited NYC for the first time and they loved it. We sat in the tavern area and they were fine with it, but if you want something more intimate I would suggest the back rooms. Both places seemed to provide professional, unobtrusive service with excellent food and the perfect atmosphere for everyone to talk and get to know each other.