Don't worry ! You and your children are covered under your husband's "numéro de sécurité sociale". If you do not have a "carte vitale" you will be given a "feuille d'assurance" that you will have to send to your CPAM.
You need to know that the rent may cost you at least 1000 € (near Paris). It depends on the place you will live. Life is expansive in Paris. Your wife will have to work ...