Am I screwing my kid over?

As soon as I got my newborn’s SSN, I opened a custodial brokerage account. I’ve been putting 100 usd into SWPPX every month for the past 12 months. When I signed up for account I put the handover age at 24. So when my kid turns 24, are we screwed with capital gains? Who pays the taxes and when are the taxes paid? Or am I just over thinking?