I don't know how "unchangeable" your hotel plans are, but, based on your desire to experience the joys of fast driving , you should check with the Arabella Grand to see if they still offer the package deal ("arrangement") that includes a suite and use of an Audi A8 with unlimited kilometers.

It's not inexpensive, but considering the "mileage" factor, unless you're renting a true sports car (Porsche, etc). from Sixt, I can't think of a better way to experience the superb German highways than from behind the wheel of a great car like the A8 (you could even take a run up to Ingolstadt to see where that A8 was built).