We are meeting family in Munich. So we thought we would use Munich as
a starting place. With having a lot of luggage, we thought traveling
by car might be easier.
When you land at MUC airport, you will be WAY outside Munich, a healthy distance to the northeast. See map below - The airport is next door to FREISING.
https://i.pinimg.com/736x/c7/f9/3d/c7f93d7d3b133730ca72a07741792c2e.jpg
https://www.kreis-freising.de/fileadmin/user_upload/Landkreis_Freising_Uebersicht_Hochformat.jpg
Not sure what "meeting family" means... family members... who live in Munich, and who will show you around the town for a few days? Or who will travel with you on this trip?
If your goal is to STAY in the city of Munich for maybe 2-3 nights, then you should postpone the car rental until you leave Munich. The car is useless within the city. There are direct trains from the airport to the city center (45 minutes away) for a low price. OR you can take a very expensive taxi ride. But either choice will be less trouble and expense than renting the car on Day 1 and keeping it in Munich. (Or perhaps your family members are able to pick you up at the airport??)
Another alternative, if staying the city of Munich isn't important: Stay at an airport hotel or in nearby FREISING, a really nice town right next door. You could either 1) pick up the car at the airport and drive to a hotel in Freising, or 2) you could take the train there in 10 minutes. Your family members could meet you at the airport or in Freising easily enough. Freising information:
https://tourismus.freising.de/en/
From the airport/Freising location you are already much closer to places I suggested you visit (Regensburg, Nuremberg, etc.) than central Munich would be.
Your family members could then meet you either at the airport or in Freising, if they will be traveling with you. It's a direct train ride.