The party and the theme look really cute.
As for the actual video, well it just looks like a typical home video. The video has little stabilization and looks like it was shot with a shaky hand. I'm really not a fan of the music choice either. I mean, I actually enjoy Lady Gaga, but I don't think it fits with a five year old's princess themed birthday party.
And since it is a home video to remember the event later on, I probably wouldn't have completely eliminated the audio in the clips in favor of a musical track (though I'm not sure if the iMovie app on the iPhone allows for this).