There is a list of reputable breeders on boxerworld as well as reputable breeders from Florida on the the Florida Boxer Rescue website.
The easy way (and many other benefits) would be to adopt a boxer through rescue that already gets along with children. Rescues get in all ages, with the average age a very young 12-18 months. I am an adoption volunteer with Florida Boxer Rescue and it is very popular for families to adopt boxers through us so they know they are adopting a boxer who gets along with children. You must be patient and adopt one that has already been around children. For example, right now we have quite a few 12 month olds that have been around children as well as adult dogs that lived with children.
I have adopted to families with babies and families with many children and it's always great to see a boxer who loves children back in boxer heaven. Boxers who love children are the happiest with their kids. If you're going to raise your own puppy around children please do your homework. Boxers are a rambunctious breed and go through stages where you will need intervene. As a rescue volunteer (in the state with the most euthanized healthy, purebred dogs) it's always sad to see a boxer coming in because it grew (much faster than the family ever imagined) and just got out of control. They are fed up and turn the dog in. Not implying that you would, just to point out that many a dog experienced family have found a boxer is more work to raise than other breeds. That being said, all of us on here, wouldn't have a home without one.
And for your family's safety and happiness, please don't take the risk of buying one off puppy finder, out of a newspaper, or in a puppy shop. If you don't go through a reputable breeder you may find you own a boxer with a very poor temperment or a myriad of health problems as it matures. Pet shop puppies are notorious for temperment issues around here, they are so poorly socialized and are taken from their litter so young.
Ashlie
Florida Boxer Rescue volunteer
www.flbr.org
owned by the rescued boxertrio - Jillian, Tulley, and Desi