You already have a high power in 7mm Mag (28 Cal).. I would go for something smaller.. Say the 243... It is great for whitetail and had low recoil for your son and has a good availability of ammo.. I have a weatherby vangard VGL with a short barrell and love it.. It is 20 plus years old now.. But look at the Rem Model 7 or Ruger Compact.. You will really like the short action and easy handeling of the shorter firearm.. I have the Ruger Compact in 7mm08 and love it..