I agree with the basic premise that the IRS is nothing to be afraid of if you make a simple mistake. Though if you make a $5,000 error (which is getting out of "simple mistake" territory), they'll tack on a 20% penalty.

That being said, audits are incredibly annoying if you didn't make a mistake, especially if children are involved. The Examinations department of the IRS is hard-headed, to say the least, and they will often make any excuse to deny you credits that you are actually entitled to. In order to get a fair hearing, you have to appeal the case to court. (The U.S. has made the appeal and court processes pretty doable even for taxpayers without an attorney, though.)