A.B.
I have worked with young children for years and have had this "problem" before...one cool trick is to teach him to give "baby hugs" by placing his finger in the baby's fist...the grasp reflex takes hold and poof! Hug! Practice this, telling him babies are too little for "big kid hugs" and each of you can practice being the baby by grasping the other's finger. Especially since you're expecting, you'll want to teach him this trick...I find that giving kids an alternative, such as this one, or other ones to show affection to a baby eliminates the problem without eliminating the affection. After all, he's just being a cutie who us doing what is very effective to show affection with kids his own age or adults...it's only a problem if you're a fraction of his size!
Good luck