First I suggest Ghibli movies:
Tonari no Totoro
Laputa: Castle in the Sky
Secret World of Arriety
Ponyo
Kiki's delivery service
Pom Poko
Spirited Away (it might be scary for some children that age but still...)
The Cat Returns
My Neighbors the Yamadas
Porco Rosso
Whisper of the Heart
Totoro will most likely will be their new favorite Mikey Mouse
Others:
Unico
Wolf Children
Tokyo Godfathers
Children who chase lost voices
Digimon
Pokemon
Sailor Moon
DBZ
Princess Tutu
Astro Boy