German public health insurance doesn't let anybody leave them just like that.
At the moment, you are running a debt with them of around 18.x% * 4,350€, i.e. of more than 783€ a month, since for people who stop being employees they always assume the highest possible income (= Beitragsbemessungsgrenze) until you prove to them that your real income is lower.
So what will happen now?
You would have to contact your German public health insurer and prove to it that you have left the country (usually by sending them your Abmeldung, i.e. the piece of paper you received when you deregistered and told the Bürgerbüro that you will move to Switzerland). This will let you off the hook.
However, your family still lives here, so your wife will have to now have to get - retroactively back to November 2016 - her own public health insurance policy. Since she isn't working, they will stick her into the Hausfrauen-Tarif, which means that they will allocate half your Swiss gross income to her and make her pay 18.x% of that half of your income. Your children will be insured for free under her policy through Familienversicherung.
For details please read: https://www.google.de/?gws_rd=ssl#q=Hausfrauentarif+site:toytowngermany.com&*