You would be hard-pressed to find a better game for $20. Great adaptation of the tower-defense genre! Fun for all ages!
The Bad: Almost 2/3's of the story mode is too easy
Plants vs. Zombies is a charming game. It's fun for both adults and children. My 8-year-old nephew loves this game, and even if he can't appreciate the zombie jokes in the zombie almanac, he still enjoys the cartoonish graphics and the accessible game-play. This game falls into the tower-defense genre. But instead of a track that you build turrents along, you use plants that defend 6 lanes of grass in front of your house. You tend the plants which keep the zombies attacking your house at bay.
This game retails at $20. This is a great price for a game that I've probably played for 15 hours. There are puzzle modes that you unlock as you go through the story mode. Some of these are rather clever; BeGhouled, for instance, is PvZ's adaptation of Bejeweled. Once you complete the story mode, it's hard to continue on with the 2nd playthrough because at that point your neighbor, "Crazy Dave" randomly chooses three of your turrents/plants for you, which is rather annoying.
Beyond that, there is hardly anything more to say about this game. It's fun, a little short, not very challenging, but it's still a fun addition to the tower-defense genre. The game also includes quite a bit of humor that both you and your children can enjoy. It works at both levels. This game is definitely worth a buy.