How old are the kids? How soon is the trip? Any other destinations in Switzerland, such as Lauterbrunnen/Berner Oberland and the surrounding mountains?
The longer legs of your trip are on the French side, so you could get a France-Switzerland pass, about $400 per adult in 1st class for 4 travel days; or half price for kids under 12. It's important to reserve ahead for the TGVs between Paris and the Swiss border, which you can do at the same time you buy the rail pass and up to 3 months before departure.
Or an alternative option is to follow Rick’s France rail travel page for the link and tips for buying “Prems” rate TGV tickets to/from Paris through SNCF (cheap, reserved, nonrefundable, available three or four months ahead of your travel date) to print at home and pay with PayPal. It does not tend to work with US credit cards, unless you have an extra level of security set up. If you go this option, you might consider a Swiss Pass or Swiss Card that matches that part of your trip; with the Swiss products, your own kids under age 16 travel free with you.