Harper will be the main character. Harper and Jasmine speak French. It takes place in London, so you can give Them either an English accent, or a French accent. Young Harper is Three, and young Jasmine is 7-10. You don't have to be that age to audition, of course. Try to pronounce the French words as best as you can. (I don't speak French fluently, btw. I've only memorized two phrases. "Let's go" and "Don't leave me")
If you get the part, I'll link you to the script.