Detroit recommendations

I went a few years ago. It's a cool town and it's amazing to see the huge infrastructure once built for 1.8 million of people now with only 600k living there.
You have to get a Coney Island Hot Dog at Lafayette's which is hilariously right next door to another Coney Island Hot Dog restaurant. Greek Town is where the night life is. Pretty crazy scene at night on the weekends. Couple of breweries to check out would be Atwater and Detroit Brewing Co. Go to a Detroit Tigers game!

Definitely check out the Henry Ford Museum. It's one of the best museums I've ever been to. Along with all types of automobiles, trains and aircraft the museum houses the chair Lincoln was shot in, the car Kennedy was shot in, the Rosa Parks bus and Thomas Edison's private collection of historical objects/inventions to name a few. Awesome museum.

There's also a few casinos in Detroit too.

Planning to go to the game vs the Mets

Just got back from Detroit / Canada trip. We did the Henery Ford museum the day we flew in, then crossed over to Windsor and stayed at the Caesars Windsor Casino. If you like museums I would say make some time for the Henery Ford. I was also told that Greenfield Village is nice, but we didn't have time to see that. Crossing the border is not bad it took 15mins going and over an hour coming back. Just make sure to tell your rental car company that you are crossing so they can stamp your paperwork which makes it easier with the car questions the agents are going to ask. Also just be prepared to answer a bunch of questions and if you stumble or take to long to answer one be prepared to go talk to another agent. As for as what to do in Windsor other than the casino I couldn't tell you we crossed around 4pm and went straight to the casino. Then left the next morning for Niagra Falls.