English speaking friends in our "German" home

It's always interesting to observe the kids when we have friends over. My youngest three speak mostly German (the minority language) to each other at home. They are much more comfortable with German. However, when friends are over, they switch to English. The other day, their friend, Jessica, came over. It was fun to watch the interactions switch between German and English. It's neat to see them really think about the language.

In the video below, I start out by asking which language Jonathan should speak. He lets me know that he should speak English because Jessica is over. They are very sensitive about which language should be spoken to certain people. Jonathan does not allow me to speak German to him when I'm helping in his Kindergarten class. But when I'm separate and the friend can't hear me, then the kids are ok speaking German to me. In this video, Simon is sitting next to me on the porch swing. Clarissa makes a comment in English "I have not do it longer" (meaning she hasn't been able to ride her bike long enough). Simon catches on that Clarissa used incorrect English. Right away, he realized that Clarissa should have conjugated the word "do". He knew that something wasn't right with the sentence and he wanted to ask me how to say the question in correct English. So, he took the incorrect sentence that Clarissa had said, translated it into German and asked me how to say it in English. That's pretty complex thinking for a 5 year old!! And yes, I realize that neither their English nor their German is perfect.

Later in the video, all 4 kids (my three plus their friend, Jessica) are sitting in the kitchen having lunch. Jonathan, can't remember the word for mustard right away and asks for 'Senf'. Later he remembers it and is able to ask for mustard. Simon copies him, but when he says the word 'mustard', it comes out as 'musters' which reminds Simon of the word 'monsters'. Then I ask the kids, in German, if they're thirsty. When I tell Clarissa to get a cup for herself and for Jessica, Jessica perks right up because she hears her name in the middle of a German sentence. I should try harder to always speak the majority language when we have friends over. It's just not polite when others can't understand what you're saying...especially when they hear their name mentioned.