I just saw this on another travel site and wanted to pass it on:
Until April 27, RailEurope is having a "Family Rail Sale" on 3-day Flex Passes and 8-day consecutive passes. Two adult passes, and free travel for up to 2 children, for $256 (instead of $434) for the 3-day Flex Pass, or $386 (instead of $656) for the 8-day pass. That is a nice discount, even with the addition of RailEurope shipping fees.
http://www.raileurope.com/rail-tickets-passes/switzerland-family-rail-sale/index.html
You have to buy by April 27, but the passes are good for 6 months after the purchase date (so you can use them this summer).
I could not find this deal on the Swiss Travel System website; it appears it may only be available from Rail Europe.
You can buy the passes in CHF in Switzerland for slightly less than the RailEurope price, but it still doesn't match the sale price. For example, 2 3-day Flex Passes bought in Switzerland would be 424 CHF---considerably more than the $256 sale price.
If I were going to Switzerland this summer I'd jump on this.