The CS credits are pooled. So you can order an adult meal for a kid.You will scan your magic band, and the cashier will see how many adults and how many children are in the room.
From that point on it's entirely up to the cashier to allow you to buy 3 adults meal.
In our experience, half of the CMs will object (but many will let you with a "don't do it again" lecture), half of the CMs won't say a thing.
We have used a small "workaround" (don't quote me, I'd deny

), not much of a workaround actually, but a way to avoid the odd cast member who would tell us we need a kid's meal for our 6 years old.
What we did is to use 2 cash register at the same time.
I went to the register with a tray with 2 adult meals on it, and DW went to the next register with a second tray, with DS in tow, and only 1 adult meal.
That way, no questions asked.
what the CM may challenge is having more adult meals than there are adults in the room.
If you do 2 transactions, you never are above the adult count, you're fine.
I don't know if it's against policy, if it's cheating, or whaterver, and TBH I don't really care.