I wish I had seen this yesterday, I have a friend of a friend who lives downtown and I saw him at a party last night.
Even so, if you two have a penthouse across from the Opera House then you will be eating and shopping in places that I pretend don't exist.
That location is fantastic. I would suggest trying "Small Plates". It is almost right across the street from you. http://www.smallplates.com/
There is a little Cuban place a couple blocks away across from the Library. That is really good and nice for a change of pace. http://www.vicente.us/
Greektown is an obvious choice. I tend to go to The Golden Fleece but most anything on that street is good. Not as upscale as the other places I have mentioned but anyplace that keep a rotisserie with a leg of lamb going in the front window is my kinda place. You can watch them go up and carve the meat off of the leg for your gyro.
The casinos have restaurants that are worth trying. Fishbone's http://www.fishbonesusa.com/ and Tom's Oyster Bar are both good too. http://www.tomsoysterbar.com/
Any of the hotels downtown have decent restaurants too. There are other places in the area but they don't come to mind at the moment.
BTW, that little park to the east of you is where the Occupy Detroit people were camping last summer.
Edit To Add: I forgot about Xocimilco in Mexican Town. I love that place but have not been there in far to long. The Botana was my favorite. Basically a vegetarian nachos but that does not do it justice. Two people can split a small one of those and be pretty happy about it.