DTW is not Detroit. There's the attached Westin hotel and a slew of safe, comfortable, reasonably priced hotels just north of the airport along Merriman road. Just stayed at the Embassy Suites and Hilton Garden Inn near the airport last week (both of which I'd recommend). Not much to do entertainment wise, but there's no reason to worried about your safety or comfort.
Along Merriman road are a number of interesting choices to kill an evening. Leonardo's (Italian) is excellent, albeit very casual. Plus, if you venture further north over to Michigan Avenue, there are (ahem) a number of adult entertainment options (stripper joints). Not that far, prob. a $10 cab fare up to those places. I worked at DTW for about a year and stayed in that area, so while you have to be a bit adventurous, there's no reason to be concerned about entertainment. I actually would recommend staying at one of these hotels if you want to get out and about; the Westin (although a far superior hotel to any of the off airport options) is very isolated and not much use except for the hotel amenities itself. Great gym in there though.