I hear many people say they just can't keep their kids interested in shooting at the range. Let's face it punching paper is not very exciting. Get a box of skeet targets, take them to the range next time with the kid. The fact that the clay target explodes when hit gets them more excited than punching a small hole in paper.
When Sky was about 12 or 13, I took him and his buddy to the range one day. I had a box of clay targets along to use in testing a shotgun I had just bought. The boys found the box in the back of the truck and took some out and stood them up against a box at 50 yards. Next thing I knew they were taking a whole stack out to 75 yards. Then to 100 yards. At 150 yards they decided the .22RF was not enough gun. By the time I was ready to test the shotgun all the clay targets had been shot. Next time at the range they took a box of clay targets and .223s. Soon they were shooting and breaking clay targets on the bank at the back of the range which is 337 yards. It was no problem to get them to move up to hunting rifles (30-06 with breaks) just before hunting season and continue to shoot at 337 Yards. In fact both boys sighted their guns in for 300 yards.
When they can hit a 4" clay target every shot at 300 yards, taking a Caribou or Moose at that range is easy. Or in your cases a Whitetail. One of the major differences between kids and adults, is that kids have never been told they cannot shoot at those ranges. They have the mental clarity, and physical reflexes to do that. And given the opportunity, and it's made fun so they can focus, they will do it. It's childs play to them.