RE: Caliber for son's first deer rifle?
As stated the 25-06' is a great caliber and is very under rated.
My first rifle was a .270win. One of the best calibers ever made.
I would suggest a .308win or a .270win.
Both are great calibers and both can be found in youth rifles. The .243 has gained a lot of popularity over the past couple of years, but I still rather have more bullet weight. I don't think you could go wrong with the .308win. You can find models that would fit him really well. No recoil. A lot heavier bullet that shoots just as flat as a .243. To me its not even a comparison.
Good luck and let us know what you get.