With kids it doesnt cost much to get top shelf insurance. This varies with companies and from canton to canton. Basic insurance (KVG) you have to get by law but all your supplementary insurance is optional. For kids you can get a semi-private room,free choice of doctor,alternative medicine, transport costs, home help an d alot more for as little 20 franks a month (on top of your basic insurance of course) so its a bit of a no brainer. IMHO it is best to get supplementary insurance when you dont need it, cos that is the only time you can get it.
disclaimer: the opinions above are supplied by someone who works in the health insurance industry