Depends what you're into. I recommend the DIA, definitely the Henry Ford (Dearborn), Hittsville, the Riverwalk is decent. The zoo is nice. If the Tigers are in town you could check out Comerica, they might even be decent this year who knows. You could do a pedal pub downtown, they even have a boat version of the pedal pub on the river. Hell bring your passport and check out Windsor. There are also casinos if you're into that. Dearborn and Hamtramck are cool if you want to explore some different neighborhoods and aren't scared of brown people. If late 20s, early 30s bar hopping is your thing, Royal Oak. If you are a hipster corktown and Ferndale. If you want to hit on cougars and shop at Lululemon and smoke cigars, Birmingham. If you want to get out to the country and do something seasonal, find a good cider mill. Early September is an awesome time of year in SE Michigan typically weather wise.