Here Jews and Gentiles worshipping together before the reigning Messiah presents a beautiful picture of the coming age. Some holidays such as Rosh Ha Shanah and Yom Kippur are very intimately Jewish in their nature and scope. These are best observed by the Messianic Jewish community and Jewish guests. Finally, teach the girls exactly who they are. They are Christians.
Christians are Gentles who do so.
Simple, clear and unambiguous. Such clear boundaries are exactly why children need as they seek to understand their places in our very complex world. It is good to be a Christian. It is good for Jews to live as Messianic Jews. God is the author of the uniqueness among people.