Are the three boxers obedience trained and socialized to people and kids? If not, please start there. I personally would not recommend you use a baby doll. It might look like a baby to us, but I think to the dog it is just a hunk of plastic that they might want to chew, and that doesn't necessarily mean they will chew your baby!
I say obedience train them and socialize them, because they are big clumsy goof balls. There way of meeting someone new might be to run up to them, maybe even jump up, or maybe rub against them, lick them, etc. They may treat the baby like a pup, which would not be appropriate either.
In addition to standard obedience, they need to understand "gentle". Work them one at a time in this exercise. Put the dog in a sit/stay, and put a nice food reward in your hand -- a favorite for the dog. First and foremost, he should hold the stay until you release him. Second, when you release him and allow him to approach the food, say "gentle". If he goes for the food harshly and haphazardly, close your hand and say "No, gentle". Put him back in the sit stay and try again, and keep trying until he approaches the food reward slowly, calmly, and carefully -- at that point you let him have it. Repeat so he understands. Shouldn't take long for a dog to get this.
I recommend letting the dogs meet the baby, one at a time of course, as soon as the baby is brought home. If you can have hubby bring home a blanket or something that is scented with the baby as you are baby are still in recovery for a few days, even better. Have hubby take the item home to the dogs, and one at a time let them smell it and as they approach it say "gentle..... gentle...... good boy...."
When baby comes home, leave baby in the car seat in a room and bring in one dog at a time. Put the dog in a sit/stay and let them just look at each other with a few feet separating them for a few minutes. If you see the dog is calm, and curious, but not overexcited, then release him from the stay and say "gentle" and guide him by the lead up to the car seat and let him smell it. If he does so gently, then say "good boy, gentle..... good boy".
I personally wouldn't recommend letting the dog stick his head all the way in and sniffing the baby, licking, etc. Teach the dogs to respect the child's space and keep a distance. If you are holding the baby and want to offer the back of the head for the dog to sniff (gently of course) that is up to you and will be fine. However, I recommend that the dogs be taught that the face/hands are off limits, otherwise later down the road they will lick the face, etc.
I have two kids and one dog. Our first kid, we didn't really do much to introduce them, and my wife really didn't want the dog anywhere near the baby. Our second kid, we let the dog be with the kid as soon as he was brought home.
My second kid has a very strong bond with the dog, whereas our first kid really does not. I think that is due to the minimal exposure our dog got to the first baby, and I regret it.
It is equally important to teach "gentle" in both directions -- as the child grows up and starts doing toddler things to the dogs, the child also has to be taught to be gentle with the dogs and respect them, etc. Teach your dogs to tolerate having ears pulled, skin pulled, toys thrown at, light hits -- because that is what kids will do.
Since you have three dogs, there is a chance that you might see some pack related behaviors. Probably not, but they might have a tough time understanding the new baby is above them in the hierarchy. Again, slim chance, but it is a chance. Another reason I say obedience train.