I would never leave them unattended, of course, but I would certainly let the boxer sniff and get to know the baby, supervised. And have plenty of treats ready, so you can praise and reward him when he sniffs and explores gently. I'd be careful to focus on positive reinforcements only, so he associates the new baby in the house with getting wonderful treats and extra attention. I wouldn't make him suddenly change his sleeping habits, that's somewhat unfair in my opinion... that could have been gradually over the past nine months so the boxer wouldn't associate it specifically with the baby coming home. But if it is necessary to make sure the baby is safe then it's what you have to do. Just give the boxer lots of love during the adjustment period!