I'm going to suggest the pump. It's one major disadvantage for a young shooter is that it lacks the recoil reduction of a semi-auto, but with 7/8 pz loads a 20 isn't too bad in a pump. I had a close call with a semi-auto when a kid, didn't get hurt, but got excited and after the first shot forgot I had a reloaded and ready to go shotgun in my hands. Another reason I like a pump even today is that when sharptail hunting, I'm often walking across uneven ground with lots of brush. I like to carry the pump with a loaded magazine, empty chamber, trigger pulled so the slide lock is disengaged. I can work that pump as fast as I can release a safety on a surprise flush it seems to me, and I like the security of an empty chamber when walking long distances over uneven ground in the prairie.
