How did 10 people (Captain, Maria, the children and Uncle Max) fit into the 5-seater car? The Captain obviously drives while the youngest sits on Maria's lap on the seat beside his...that's 3 out of 10. Did they pile two people on top of someone on the back? Or stuff someone in the trunk?
Unless you consider that Maria could've been holding Marta and Gretl (one arm around/across each. That's 4 out of 10.) Liesl could've had Brigitta, who's 10, on her lap also. Or Louisa takes Brigitta, Marta goes with Liesl. At any rate, nobody said escaping a soon-to-be-fascist country in a 5-seater was a picnic.
Could Maria even handle having two kids on her lap without going numb? I saw Gretl on Maria's lap at one point, and nobody on the Captain's. Maybe four people (Liesl, Friedrich, Louisa, Max) squished into the three-seat space at the back, and the remaining three took three out of the four laps? Would Kurt sit on Max's lap?
Why should Captain von Trapp expect that Herr Zeller, the local Nazi official who is obviously in close contact with Berlin to know that he has been ordered to sign up with the German Navy? The telegram ordering him to report was an official order, not a private telegram.