To hunt in PA (12 and over) you must take a hunter's safety course prior to purchasing your license. Children 11 and under can hunt certain game (small game included) if accompanied by a properly licensed adult hunter under PA's Mentored Youth Program. A Mentored Youth license is about $2.50 if I recall and can be purchased on line.
Even you, as an adult, must show evidence of having taken a Hunter's Safety Course.

Classes are still available this year. Just go to the PGC site and look under the "education" tab. You can both take the course together.

For a first shotgun I'd recommend a 20 gauge pump - Either Remington or Mossberg. You can always load one shell in it and use it as a single shot until you think he can handle the weapon safely.