A new gun is going to collapse in value. You're better off buying a used one and then having it restocked and fitted to you.
The only way your kids are going to make money on the guns is if they hold on to it for 50 years. Even then, they would be better off with a nice index fund.
You're H&H is going to come back from Africa as a $75,000 (US) rife - at the most. And it won't be as nice as an older one, either.
Here's one that you can get a much better deal on:
http://www.rbsiii.com/collection/rifles/H&H_375flanged/H&H_375flanged.htmOWD