If your 12 year old truly eats like a grown up the deluxe plan might make sense, but it is very expensive.
The deluxe plan made sense for my family when both kids were under 10. We'd do a sit down breakfast and a sit down dinner, had quite a few Signature meals, occasional sit down lunches (which we'd sometimes split to save credits for those Signature dinners, and we weren't often that hungry anyway) and at the end of the trip we not only saved money compared to the same meals out of pocket, we also had a ridiculous amount of snack credits we'd use to bring back packaged Disney treats, stuff that'd last at least a few days (like rice krispie treats) or a while longer (like the giant bags of Chip and Dale trail mix).
If by having breakfast at the hotel, you mean in the food court or the counter service location, the regular plan would make sense and the deluxe plan would not.
I'm not sure the Quick Servicee Dining Plan makes sense for anyone unless a: they're using it for lunch and dinner and b: including an alcoholic beverage with both meals. QS breakfasts are usually no more than $16 with a coffee or non-alcoholic beverage and if you're drinking that early, bless your heart. Plus, assuming you're getting breakfast every morning at the hotel's QS location, the regular dining plan includes a souvenir mug so you won't be paying for coffee or tea anyway, you know?
So I think
@Kingdom Konsultant makes sense. Book the regular plan, then make your reservations, if you start piling on a lot of Signature meals, or buffets or other restaurants with a fixed price, the Deluxe plan might make more sense. Or if you start booking breakfasts in the parks before they open, so it's a sitdown breakfast and a sitdown dinner, the deluxe plan might make sense.