Meerhaba is the Turkish greeting, similar to Arabic. They are cute and pick up all sorts of stuff from other children.
It is a fantastic way to learn a new language, and as I learnt to speak French fluently, I spoke to my son French from the time he was born, whilst my ex husband spoke English. Obviously, when we were together as a family we spoke English. He was not totally fluent and has forgotten quite a lot now he is an adult and does not use it all the time, but it certainly helped him at school. He was yards a head of the other kids.
French, like German and other languages have a structure that English does not for using verbs etc. It is a very good discipline and kids love these kind of disciplines and not only that they can show off to their peers. By the time he was 10, we had informal classes at my house 2 or 3 times a week as his friends wanted to learn to, including one who was bi-lingual in English and Italian.
So, please encourage it. After all, no learning is ever wasted.