My son always loved, and still loves, babies. When he was two, I got him a small baby doll. He didn't dress her at that age, just carried her around and loved her. If he left her somewhere, he would remember and call out for his baby. So, I bought the baby a stroller, but he never played with that. One day I folded up the stroller, it was like a stick on wheels folded up. He grabbed in and pulled it along and said, "vroom vroom truck." He is definately a boy, but he will be a loving, attentive, nurturing dad someday. If boys didn't like dolls, they wouldn't make the GI Joe dolls. Some men, and women, feel better about their son playing with dolls if it is a man doll with fighting gear.
Another point, is that boys do like pretty things. At some point, they like pretty girls. :)
I think it is great that your "hub didnt seem too bothered by his son playing with dolls." He is comfortable with his masculinity and doesn't feel threatened by his son playing with dolls. All the better for your son to grow up to be a great dad! If you are worried at all, get him a GI Joe doll and phase out Barbie, if ds will let you.