We're using Latin for Children and LOVE IT! There's a Spanish and Greek version that are identical in format, so although we haven't used them, I still feel comfortable recommending them. www.classicalacademicpress.com
Yes. I can only speak of the latin one, but it looks like the Spanish is the same. You absolutely have to have the student primer and the DVD set. The answer key is optional (depends whether you think you'll need it or not... I use the Latin one all the time simply because there's more than one right answer sometimes, and I'm not sure what they're asking for or why).