I'll put in another recommendation for Minimus Latin! When my 7-year-old came to me and said he'd like to learn Latin, I was little baffled. I wanted a program where he'd feel like he was learning, but that also wouldn't take a lot of time each day. I also wanted something more hands-on and engaging. It took awhile to find something that wasn't geared towards middle school/high school. Minimus Latin is rather pricey, but well worth the investment (at least for us). I purchased the audio CD and my boys started picking up on Latin phrases right away. I've been using it for three years, and my youngest enjoys making up stories in Latin to confuse his older sister (who chose to study French independently instead). Since it's published by Cambridge University Press, they sort of speak Latin with a British accent, which is hilarious. They're in 4th/7th grades using Level 2 now.
If you purchase the teacher's manual, it includes a variety of extra study options (art, music, history, etc.) There are also worksheets in the appendix. All of that is optional though. You can use the stories and the exercises in the student book. If you know a little Latin, you'd probably be able to translate the stories. But I've liked having the teacher's manual for extra study suggestions (especially if you're looking for ideas for a multi-sensory, or interdisciplinary, approach to learning language).
The only real downside I can see is the cost. I've been able to find it used from Ebay and Amazon Marketplace, but I've had to purchase all the parts from different sellers. I paid more for Level 2 than Level 1. But I did eventually find a decent price! We're using that level for two years instead of one, since I didn't feel that my youngest was ready to move up to a middle school text yet.
Another critique might be that it isn't really designed for mastery, but more of an introductory course. I think you could use it for mastery, by having your child memorize vocabulary and grammar rules. But the lessons aren't really designed with that purpose in mind. It builds on concepts over time (the second book is definitely more challenging than the first!) My boys couldn't necessarily decline a verb or tell you what the case endings are. But they usually end up using the grammar correctly when they make up stories. I think by listening to stories they're learning the language in a more natural way--like how we all learn to speak before we study grammar. I guess you could actually count that as a strength of the program, rather than a weakness? It depends on what style of language instruction you're looking for.