So what's a cognate? It's a word in one language that resembles a word in another language, usually in how it's spelt. A thorough explanation of list of cognates is at the link in this post.
As is applies to teaching kids, I like to start with topics that interest them, like animals. And, since the word for animal is animal (ah-nee-mahl), this cognate provides an easy introduction to that topic. Some of the first ones you could start with is elefante (ahl-ah-fahn-tay) for elephant and jirafa (hee-rah-fah) for giraffe.