I put together a potential route for ya.
https://www.strava.com/routes/11731367
+1 on Johnny Noodle King. Lots of food options these days in Detroit.
This route swings by the old Detroit train station, belle isle, river front, Indian village, Belle Isle, gross pointe, etc. There are plenty of side options in Detroit (Whitney building, Velodrome, Eastern Market (great food too – I never go on a bike tour without hitting local outdoor markets), Dequindre Cut.

A lot of the empty industrial areas are actually pretty good for riding – zero traffic. Generally I like riding in Detroit proper rather than the suburbs because suburban routes are crowded with traffic and Suburbanites can be pretty intolerant of bikes.

The loop around Detroit that I posted would be basically car free – mostly on dedicated bike trails. But if you want to get a feel for the city – go right through town (on a weekend). Most of the really bad areas would be away from the city core, and away from the river area (if the abandoned industrial areas don’t bother you – again the roads are in rough shape (think pinch flats) but there are areas with no automobile traffic).