Buy them a copy The Barefoot Investor
Can be worth its weight in gold, especially the example of Einsteins “The power of Compounding Interest” and the advantage of starting young . If they at least learn that, and take it to heart, it will be well worth while.
they always commented on how there were just a few central ideas surrounded by a huge amount of "fluff"
Yes, there are just a few central ideas; for value investors ONE MAIN REASON that (some) shares increase in value over time.
Peter Lynch, in his book published decades ago "One Up On Wall street" devotes an entire chapter to it.
Main thing is that they fully understand what those central ideas are and more importantly , put them into practice.
you will generally be heavily taxed (45%) once you have much more than $8,000 invested under a kids name.
A few managed funds have a "Dividend Substitution Plan" where dividends are paid as new shares; zero tax is payable until/unless they are ultimately sold, that would have CGT. There are no Brokerage, Commission or costs.