It sounds like this may be your first overseas non-rev trip. So far, this is what has happened to us on Delta. We've saved a lot on airfare, but issues have kept it from being free.
Non-rev #1. RT Seattle -- Paris. That part worked fine. But I got stuck in Salt Lake on the way from Tucson to Seattle the day before our flight. I spent the night and "bought" a last minute ticket with credit card points. That got me to the airport in time the next day to meet my husband and make the Paris flight.
Non-rev #2. RT Tucson to Amsterdam. There was no space for us on the early flight from Tucson to Atlanta, so we missed the first flight to Amsterdam. We got on the second flight to Atlanta, which should've gotten us there in time to make the second flight to Amsterdam. But a combination of late arrival, unavailable gate space and people who blocked the aisle, even though the flight attendants asked them to stay seated while we came thru, caused us to miss it.
We ended up having to spend the night in Atlanta and were able to get on the first flight to Amsterdam the next day. When I was sure we'd get on, I contacted both the owner of the apartment we were renting and the rental car company to let them know we'd be a day late. We ate the costs of that lost day.
There was a third, later flight the day we were originally supposed to go to Amsterdam, but it was a KLM plane, not Delta "metal" as they say. My understanding is that the flight privileges are usually only for the airline that employs your relative.
Non-rev #3. RT Tucson to Rome. We got on our scheduled planes with no issues. Of course, this time I planned to get stuck and we got there on time without any hotel reservations. Our idea was to lose the jet-lag in Fiumicino before flying on to Istanbul (points), but the place I wanted to stay was totally booked. Where we stayed wasn't great, but there was a very good restaurant adjacent, so we coped.
After Istanbul and Greece, we flew back to Rome (points) with a secure reservation at our preferred place in Fiumicino. We were due to fly home from Rome the next day, Wednesday. No room. That went on for 5 days, and our son didn't know how to fix it. Every day we packed up and went to the airport. Every day we went back to our hotel to check in again. Fortunately, our hotel had plenty of room and sympathy for us.
During that time our trip insurance expired, my husband ran out of one of his meds and we had to call our credit union to get our cards extended until we got home. We went to a pharmacy and got enough of his med to last for a few days. We hoped nothing would happen that required the insurance.
On Saturday we learned that the flights from Milan were almost empty. We tried again on Sunday. Nada. We decided that if we didn't get on Monday, we'd take the fast train to Milan, spend the night at the airport and fly out on Tuesday. We didn't, the desk agents wrote us new passes, we got our train tickets and headed north. In spite of all the drama, we still saved the equivalent of one RT ticket.
Instead of flying back the way we flew over, we went Milan -- New York -- Salt Lake -- Tucson. A couple of women who had flown non-rev Atlanta to Rome also got stuck, but they had higher priority than we did and were able to get on a Rome -- New York -- Atlanta route on Saturday.
Hopefully you won't have any complications like we've had. But, be prepared with alternate plans just in case. You are going to a very popular place at a very popular time. It might be worth the cost to schedule a hotel for which you can change the arrival without penalty, or that is cheap enough that you can absorb the cost if you don't get there on the first day of your reservation.
P.S. I wouldn't plan to arrive in Munich jet-lagged and head straight for the beer...
