Glad to hear mom and baby are ok Lee!
Unfortunately, fractured collarbones are not all that uncommon in cases of shoulder dystocia. Being post term increases the likelihood of it happening because after about 37 weeks the baby gains about 1-1.5 oz per day, and the bigger the baby, the higher the risk of the baby getting "stuck" on the way out. As you mentioned, it will take a couple of weeks to heal. He should have a follow-up x-ray in a couple of weeks to make sure it's healing properly.
Maybe your daughter can find out from the paediatrician if she can give him Tylenol to help with the discomfort. Our hospital has a policy in place for newborn pain control in cases like this. Normally we make sure the baby's arm is well supported on the side of the collarbone fracture, and swaddling baby should make it possible for everyone to enjoy holding him without worrying about hurting him.
Congratulations!
Love, Scully