www.mndriveinfo.org but you need the actual driver's license number to check. I wouldn't worry as much about the license as worrying about if there is insurance on the vehicle. Ask to see the insurance card.
Anyone can type in a drivers license number at the Minnesota Department of Public Safety website to see if it is valid according to their records. I can't think of a way that a drivers passengers could suffer as the result of the driver not having a valid license. On the other hand, if the vehicle driver is also the owner, and there is no insurance covering the car and its occupants, that could be bad for the passengers in the event of a motor vehicle accident, especially with an underinsured or uninsured other vehicle-driver. Why? Without insurance coverage, they might get less quality medical care, and may not be able to recover for pain and suffering and other damages.