Love the idea Lene.
I recommend to write as you speak - that way your voice will be preserved as well. Try and keep it light with funny stories (i'm sure you have plenty, having made the transition myself). Tell it as it was, as you remember.
I wouldn't worry too much about a childrens version - they grow up and you wouldn't want them not to touch the story again.
Maybe leave room for future generations to include their experience in case they are going back to good old Germany and experience what you have written about.
Good Luck and have fun writing.
