Middle name after step dad

I want my sons middle name to be after my step dad, but my bio dad is still in my life. My bio dad and I are on decent terms. He never did anything wrong he just was never there. Within the past few years he has started to make an effort, but I will never look at him as a father. My step dad has been around for a while now and has really treated my sisters and I as his own. How do I go about naming my son after him without totally offending my dad? I know the second I tell him that my sons middle name is my step dads name, it’s going to get awkward. And my sister (who is close to my dad) will give me shit for it too. I thought about saying that it’s a name on my husbands side of the family too? Idk.