22lr : Tikka T1x
223 : Tikka T3x Stainless SuperVarmint or SuperLite - depends on if he walks or stationary shooting.
308 : Tikka T3x Stainless SuperLite
Tikka Ringmounts or Sportsmatch rings
I prefer Kahles or S&B scopes.. but they can be a bit expensive.
Upgrade to McMillan stocks later if you want them to be a "for-life" rifles.
If you have all of those, please sell them to the kid's dad for $1,800, the limit stated in the OP. And yes, that includes scopes and mounts.
