myfreedom, even though they've begged you not to tell him, I don't think you have any choice. I can understand that, when the time comes, there's a lot of pressure on them not to make a fuss and just hope for the best, which means not allowing them to be put in that situation.
Can you imagine him running that red light and the whole car being collected by a truck?
It's not just the DUI and endangering his own children, it's also the shocking fact that he tells them to keep it from you.
Really strong action required from you. He's been lucky so far, but it may not last forever.