Son's father has been absent for so long...

He doesn't deserve it, but putting your son's interests first is a very generous thing to do.

If you could will it that the father becomes a part of his son's life, would you? Should a parent be given a second or third chance to step up and do the right thing? If you deny access to your son and if your son ever finds out, and he will, then you will be forever the "bad guy", in his eyes, for not letting him have a father. The only reasons to not allow the father to come is if he is a pedophile or druggy. Also, if he develops a pattern of coming and going every few years and never actually being a parent, then he doesn't deserve access. Oh, and get the courts to enforce child support payments. Retroactive. It's the father's responsibility and obligation. VOE

Seriously after that long a time he should just stay away, you're better off without him!