What's a good animê for 12 and under?

CardCaptor Sakura

My first animê when I was little and the best magical girl animê in my opinion <33

Pokemon.

other than the ones that have already been mentioned, i recommend Fruits Basket and Shugo Chara.
also if you'd like to try out shounen animê to give yourself or the concerned person mais exposure, i'd recommend Inazuma Eleven.

Hmm... Aikatsu might be what you're looking for. It's definitely got the girly part at least.

Maybe some like Sailor Moon, K-on, or amor Live: School Idol Project (if you want the girly one)
Not so girly one, maybe Pokemon, Digimon, Beyblade, yeah something like that.

Wedding Peach
Mermaid Melody
Cardcaptor Sakura
Phantom Thief Jeanne
Any series from the"Precure"franchise
Lovely Complex

Capeta was pretty good for me at that age.

You could watch Powerpuff Girls Z. It's literally Powerpuff Girls but with Japanese animation.

Pretty cure / glitter force! And don't forget glitter force doki doki! On Netflix now!