30-06 still burns about 20-30grn more powder and lobs 40-80grn heavier bullets to do the same job - with harder management - than you COULD be choosing...
You're trying to accomplish two things, so it's really up to you which one is more important - and you asked for opinions about the 300wm as a tool for learning long range, so forgive those of us who took you at your word in both counts. You're trying to 1) buy some whimsical piece of history by getting a Remington to pretend it's somehow related to an M24, AND 2) you're trying to buy something to help you learn how to shoot long range. These two goals are grossly contraindicated, but being in your inexperienced state, don't understand the conflict - but your responses in the thread have shown the prioritization of these two, and now we've arrived at a trivial solution... which is to say, a non-solution to your original query.
So in this case, don't ask questions - you don't listen to reason on "what should I buy to learn long range shooting with my son?" because you're ONLY focused on buying some Rem 700 Long Action so you can pretend it's an M24. It won't be, it'll just be some run of the mill rifle from a new company with a Remington label on the side, still have all of the issues we've all spent money on R700's and CUSTOM 700 clone actions for years to fix, and like
@Frulk, your rifle will sit in the back of the safe for years until you eventually sell it because it's not the right tool for the task of learning LR shooting, so you will have to be fully satisfied in your (apparently) more important goal of owning a Rem 700 Long Action so you can pretend it's an M24...
So just go buy the 300wm Rem 700. It won't be fun, it won't be productive, and rather than bonding over this new activity with your son, you'll both lose interest and the rifle will gather dust until maybe you decide to sell it...