You may already know this but getting 12V out of a 15V PD is relatively straightforward with either a linear regulator (less ripple but less efficient) or a buck converter (more ripple but more efficient). The Internet is full of very inexpensive boards that do all that.

I disagree. 12 V is not that much for an adult when you put it on your tongue, but with today's ubiquitous technology in everything, a toddler that puts everything in his mouth, will lead to a lot of distress and fears. I prefer the existing 5V. I suspect you are young and still not a parent.

Also, as a hobbyist, you can pretty much get a cheap PC power supply and transform it in a very professional "every volt and power under the sun" power supply for your hobbies. That's what I did.