Mea culpa, mea culpa, mea culpa. Well, not really. Given the lack of any back story in the original post, my impression is still the same.
Ken, thank you for your second post. The example of the girl in Michigan certainly shows it can be done. Sounds like she had the experience and background to be up to the task. Nothing mentioned by ksc01 led me to think this 7 year old is an experienced shooter and hunter, but I could certainly be wrong about that. Seems like asking the PH/outfitter for his recommendation/ requirements for a suitable caliber would be a really good first step.
I've said more about this than I should have, so I'll leave it right here. It would be great to resurrect this thread in October with hunt report from the OP.
Steve