How can I tell my kids the real story of Santa Claus in a way that they will understand?

My youngest son has just found out that Santa isn't real. I would like to tell all 3 of my kids the real St. Nick. I have been to several web sites that tell the story. I want the story told using words that my 6 and 7 year old can actually understand. I read the story on these web sites and my kids have never even heard some of the words that it has, let alone know what they mean. I want to tell it kind of you would see it in a child's story book. I just want them to know that he was a real person at 1 time, when he lived, where he lived, who he was, and some of the things he did before he died. I would really appreciate this info.