I agree with the other posters that a later flight would be better if trying to connect same day. They may end up rushing and still miss the flight.

Your parents may want to reconsider staying with their original plan however. Due to the time change do they really want to be taking off from DFW to go back home at 3 or 4 am German time? There is a Grand Hyatt in Terminal D that is nice and would be easy access for them after they land.

Perhaps they’ve already thought about this but wanted to put it out there.