Should I keep them involved or move on without them?

okay, I have a son who is 3 1/2 years old, his dad and i were more like a one night stand and i found out i was pregnant, i didn't hear from him until about a week after my son was born, i sent him a picture and asked if he still wanted to do a paternity test, he said that he knew that my son was his because it looked like him. he told me he would send me money every month. well that was the first month, then he stopped...i took him to child support and now he pays a mandatory amount...okay..fast forward...

i went to take my son to visit his side of the family, which is my son's grandma, aunts, grandpa and all that good stuff, it was terrible hosting...they barely paid any attention to him, the mom & sisters do send him things although its late, they send him stuff for his birthday and christmas, as for the dad, HE IS NOT INVOLVED AT ALL.. well here is the thing, i live in hawaii, they live in memphis, after my terrible trip i have no plans of making my way back there ever. well now, on myspace, my baby's dad new girlfriend was keeping in touch with me, i keep telling her i can't stand him, because he was never involved in my sons life, and i want nothing to do with him or his family...but then i always get confused, because i don't want to sound selfish, but i want to know if it is even worth it. my baby's birthday is coming up in june, i haven't heard from them for over a month...so what should i do? should i just leave them alone, not bother with them and lose all communication or should i keep them around? PLEASE I NEED SOME INPUT...