Depends on what is the age group, what are their tastes, and what is your personal opinion on children watching things like violence or emotionally disturbing content. Personal favorites for me from popular films are:
- anything by Pixar
- anything by Tim Burton
- anything by Hayao Miyazaki
- Lord of the Rings
- Xmen
- ET
- Lassie
Also there are quite a lot of tv and old films about children and animals, just you have to find them as you go. I recommend
- The journey of Natty Gann
- Flash
- Iron Will
- Andre
Another title I would recommend for older children to see is "The Devil's Backbone" (El Espinazo del Diablo) -- people may dislike because its quite violent -- but it addresses issues sensitive for children, like bullying.