Hi Sarah,
I have had two boxers and they both have been great around kids including babies. Although, my first boxer liked to jump up and rip the ribbons and bows out of my little cousins hair, accidently knocking them down but she never meant any harm, both of my Boxers let kids do anything to them, pet them, sit on them, pull their tongues, ears, anything really. I don't think you will have a problem.
Just tire your boxer out in the Metro Parks, its a great resource we have here in Cleveland for our beloved boxers.
Take Care,
Nick