I'd check into the Kempinski and then take the S8 into town for a few hours - Marienplatz is a good central place to get off.

Check the schedule for your day before your trip. There can be track work on nights/weekends, and it isn't uncommon for the S8 from/to MUC to end at Ostbahnhof during those times, meaning you need to transfer there to another train - probably the S. Not a huge deal, but just one more step. Today the last direct train is departing Marienplatz at around 10:30, but when I look at this Saturday I'm not seeing any direct trains the entire evening.