The Von Trapp family could not have escaped over the Alps. If they had, they'd have been headed into Nazi occupied territory! The real Von Trapp family escaped through Italy while pretending they were on a skiing holiday.
In the film, the Von Trapp butler was a secret Nazi who blew the whistle on the family when they attempted to push the car away in the middle of the night.
In reality, this butler was a Nazi, but he actually helped the family make their getaway during the vacation.
It wasn't the butler who blew the whistle, it was Leisle's boyfriend Rolf. And he blows the whistle in the church grave yard. Franz was also a Nazi, but didn't stop or help the Von Trapps.
Actually, you're all wrong. All you have to do is read the notes that come with the soundtrack cd, and you'll find that the von Trapps actually escaped Austria by going on tour around Europe as the "von Trapp Family Singers." They raised money, then came to America, where they built the von Trapp lodge in Vermont.
I don't think five309 means it as literally blowing the whistle, its meant as ratting the family out to the Nazi. You see in the film the butler looking out the window as the family push the car out the gates.... obviously its meant to indicte that he's contacted the Nazi. What five309 is saying is that in real life he help them escape not rat them out. Hope this clears things up.