I need some advice please.... Baby Daddy Drama (kinda)?

So 3 years ago I was with a guy and I found out I was pregnant 5 months in the pregnancy he splits. So i have been raising my baby boy alone, with help from MY family only. Now just last night i get this phone call from the (sperm donor) and he wants to see MY SON. I am in a bind cause the past 2 years i said I am so happy I didnt have to share, or worry about the baby daddy drama scenes if you know what i mean. So i am in limbo should i let him see the baby as just a friend i will not push him to call him "daddy" cause he isnt one or should i just say NO... You had 2 years and now?? i am just so confused i dont want my son in 10 years to hate me for either 1) letting him in his life or 2) not letting him i just dont know how good of a role model he is especially by walking out on his pregnant girlfriend in the beginning... Please help me