We have used Latina Christiana by Cheryl Lowe. You watch a video and then complete a workbook and study flashcards. My DS hates watching the videos because they are slow moving. However, it has taught him a lot about Latin, so if the goal is to learn Latin, I would recommend it. If the goal is to have your child enjoy the process of learning another language, you might want to explore other options.
A very beginner level program is SingSong Latin. It would allow your child to move rapidly through the Latin basics, however it really only covers the language at a very superficial level. I guess you could say it's a Latin primer.