For a youngster that .243 will shoot much easier than the .30-30. The .30-30 in lever action will bea very light rifle that will kick hard. The .243 will be a heavier rifle and will be easier to shoot as a result.

On the other hand, if your deer hunting is primarily in deep woods with snap shots and short range, a lever action .30-30 may be more appropriate in spite of the heavier recoil.

Be advised I'm referring to felt recoil, which is all that really matters. Shoot a Winchester .300 Magnum in a 20 LBS rifle and it would probably shoot easier than a .243 in a 7 LBS rifle.