A good friend of mine was in a similar situation. He was separated from his wife and they had three kids. She was already shacked up with someone else (in front of the kids). He met this very hot Asian chick and after a couple of years decided he wanted to marry her (while he was still just separated from his wife). He then went back to his wife and told her that. The wife proceeded to turn it around on the spot and asked my friend to go back with her for the sake of the kids. He decided to do it. I believe that he has been very happy and has not regretted it and has gotten over the Asian chick. The Asian chick apparently had considerable sexual talents which he decided to leave on the table.
I don;t know if this helps but my feeling is that you could do either one and make it the right decision. But the bottom line is if you feel that your son would have a great benefit you should consider a trial run with your ex. I wouldn't commit to it until you have lived with her for six months or so.
Whatever you do Ragu, believe what YOU think is right. Right, for you, for your kid. If things were broken before, it can be fixed. You're a different person from what you were a few years ago. Always said there's no greater story than watching the villain become the hero. Good luck bro.
How did the ex suddenly get back in your life? She just picked up the phone and decided to call and say we should give it a shot? What's her angle? She just get dumped? Something smells fishy, and it ain't her twat.
Ahh catching up on the last four pages was fantastic. My two cents: They are both good looking gals, but it sounds to me like you look at the current girlfriend as more of a long term fling and the ex as something you wish had went differently. From the information I have I'd suggest continue the fling and stay great friends with the ex. When you grow up you can have nice things again.