Kids can use gift cards, and if you do use a credit card for an account your kid (or spouse... or parent) is using then you can remove your card after the purchase.I've been doing it for years, on a few different platforms, with no issue.

That said I do wish there was an easier way to say "don't ever save my card info" It's clearly a dark pattern, and I routinely get furious about the loopholes I have to jump through .