That's just south of the river. There are lots of interesting places within a few blocks of there, that still ought to appeal to most folks. Piccolo Sogno Due is a great new Italian place on Clark (walk along Wacker to Clark, then cross the river), and Sable is always excellent, contemporary American in a small plates format (and great craft cocktails too). The Purple Pig is nearby too, but they don't take reservations and waits to be seated can be horrendously long (and it may be a bit risky for the person whose tastes you don't know).
Another place that might fit your particular situation is Aria, in the Fairmont Hotel nearby. Much of the menu is pan-Asian, but they also have American standbys like steaks etc for the picky eater (or someone whose tastes you don't know). You could also go with a steakhouse - not creative but may work; nearby choices include Chicago Cut Steakhouse, Petterino's, Morton's, etc. And for seafood, Shaw's Crab House is nearby.
If you wanted to try high-end haute cuisine, Sixteen, in the Trump Hotel, is right there as well. But that can be a real crapshoot for someone whose tastes you don't know.
All of the above are open on Mondays.