Hi Ben, just wanted to say we set up our 15 y.o. daughter back in April in the exact same way, and it has been a highly rewarding (no pun intended) learning and bonding experience for her (and us). I highly recommend working through Sean’s “Six Keys to Financial Success” with her along with watching a couple of basic videos. CAJ, E, and SAN are incredibly cheap right now.
We followed this exact advice from Sean at the time plus a defensive position (SLV was low back then), and I walked her through how to set up her Market & Limit buys and spreadsheet to place all her tranches. She started in 4 positions, but she now has a 5th position due to profits (16-51%) from selling 3 positions + 1/2 her SLV. We auto fund her account at the beginning of each month with 1/5 of her monthly allowance [to go toward her college savings (1/5 to tithe, 1/5 to gifts for others, 1/5 to non-basic clothing, and 1/5 to discretionary)].
Wishing you tremendous success as you embark on this wonderful journey together!