If you are familiar with Carnival Games, then "Birthday Party Bash" will be very familiar to you.
This is basically a series of mini-games for kids with a birthday party thrown in as a way to connect everything. Before starting, your child gets to choose the theme for their party. Then the fun begins- the more games your kids play, the more "components" they get for their themed party room- decorations, party hats, special chairs, presents, and cake. (There's also an option to play the games one at a time without the party, but we liked the idea of moving from game to game without having to pick what comes next.)
The mini-games are cute, but I found their range a little strange. Some were very easy for my almost-four year old to play, and others, which *seemed* simple, wound up requiring lots sweat and concentration from my husband to just complete. The game does point out winners, but very discretely, so that kids of all ages and skills can play together and celebrate. The basic goal is to finish each little game so that more prizes for the party can be earned.
Sometimes the game screens were a little confusing, too. For some games it would break into four separate screens so that each player had their own space to complete the task, and for others, the four players share the screen. These were the hardest for my daughter at fist- there's no clear designation which pointer belongs to which player, so at first there's always a bit of scrambling around trying to figure out what's happening.
The birthday party is really nothing special. It's certainly cute, but definitely not a "birthday party in a box" as is suggested. I would not advise chucking out all your big party plans and inviting some of your kid's friends over to celebrate with this game. The graphics are cutesy, but not mindblowing.
Also, you can't use Miis, which kind of stinks. My daughter LOVES her Mii and it's sort of a connecting link for her between the few games she can play. It's disappointing to get a little avatar instead. There's not many of them to choose from, either.
Overall, this is a great title for kids. For the smaller ones, be prepared to help out a bit starting up the game, choosing options, and as they navigate from game to game. I'm not entirely sure that my daughter will choose and start up this game on her own (she prefers the two Diego games and the Dora games- she can start and play those completely on her own) but I think if we put it in for her, she'll really enjoy it.