He confessed to his children who were officers in his company and legally required to go to the authorities or face criminal liability themselves.

You're right. I was thinking of the 3 months between the arrest and the sentencing, not the collapse and arrest. You'll have to forgive a memory 13 years hence. ;)

Madoff was also planning to cash out and distribute the money he had left to family and friends. The FBI probably acted to prevent that

And he confessed everything to the FBI when they first talked to him..