Can a 53-year-old promiscuous guy really change?

Twenty-five years ago, I was with a divorce who cheated on me and we parted ways. He contacted me 8 months ago and says he's a changed man (at 53)--now he wants to marry me. He has a good job and house, so he's not after my resources. To mention, he says that during the past twenty-five years, he's not had any committed relationships--he's been picking up many women at work and a local country & western bar. He's not had a religious conversion, so I'm worried about his ability to commit. I'm 48, have a 9-year-old son and this guy was my first "true love"; hence, I'm worried about my judgment becoming skewed by latent nostalgia and the fact I still find him quite desirable. Please share your thoughts--I don't want my son or myself to get hurt. Thank you.