Great film, slightly questionable in parts.
Overall, it was a great film. Hilarious, lots of fun to watch. Parents should know a few things, though.
Violence: lots of peril. The film is based around chickens escaping a chicken farm, where they "lay eggs, day in, and day out, and then they kill us". A chicken is sent to the chop (off-screen, a 'thud' is heard). SPOILERS: later on in the film, the owner of the farm prepares to transform the farm into a chicken-pie farm, threatening to kill all the chickens. Attempts to kill one chicken with a knife, however the chicken escapes.
Swearing: Not really. Some may be uncomfortable with 'poppycock', etc.
Alcohol/Drugs: No 'drug' use, as such. There is a scene where some chickens pretend to be drunk and drink 'cocktails'.
Sex: There are a number of innuendos that would likely make the film PG if it was released today ("Why did you come here?" "Why, because of all the English chicks"... "You know you are the first chick I met with the shell still on?"... etc). Something to be weary of.