As long as the dad is responsible parent that takes well being and security of your son seriously then your son will benefit from having both parents in his life. They both can teach the child about life from different perspective and provide relationship that helps with emotional development. The dad has also right to have his son as part of his life given he can fulfill his basic parenting responsibilities.
Do you have good communication with your former partner? Is he honest, trustworthy and reliable? Is he emotionally stable and has safe environment for your child?
I think these are the important questions to ask and think about.