The couple has enough money to make each of their three children billionaires if they should want to do so, but as they answered, that's not the plan at all.
"We want to strike a balance so they have the freedom to do anything, but not sort of a lot of money showered on them so that they can go out and do nothing," said Bill Gates. "They need to have a sense that their own work is meaningful and important."
Wired calls it the "anti-Paris Hilton approach."
The Gateses came to this attitude on child-rearing after reading an article by Warren Buffet before they were even married. The takeaway from it was that you don't do your children any favors when you make them instantly rich.
While it's unclear which specific article they read, you can read this recent interview with Mr. Buffett that delves extensively into "Buffett family values," which he describes thusly:
Our kids had a very normal growing-up. I mean, they've only and I've only lived in one primary house that I've owned in my life, and I bought that in 1958. So they did not see us moving into progressively fancier houses; they did not ride in private planes. They went to school on the bus. Every member of the Buffett family in Omaha has gone to a public school. They went to the same school that their mother had gone to. They went to the same high school that she'd gone to.