It's worth watching, it's a far better animated film to take your children to than another that I could mention, and it might even be something to revisit every year or two.
Anyone watching it is still going to have fun, though. The sheep are hilarious, the antics they get up to are wonderfully humorous, and what might keep the adults focused is the appreciation of the craft of creating these scenes. Stop-motion animation is incredibly time-consuming, and many of the best moments in Shaun the Sheep Movie act out like intricate Rube Goldberg machines. Watching the pieces being set up and knocked down is a joy unto itself; that the act is combined with a charming sense of humor is what makes the film so much fun.
It's really the difference between warmth, heart, and creativity and the annoying repetition of something like Minions. The two films, released in North America so closely together that comparisons are almost inevitable, suffer from many of the same problems, but Shaun the Sheep Movie is far funnier, much more charming, contains significantly better animation, and despite its characters not speaking a single word of English, makes them far more emotive and understandable. It's amazing what a difference creative and talented filmmakers can make for a project.
I wish there was more to Shaun the Sheep Movie. I wish I could remember more than a handful of moments. I had a lot of fun while I was watching it, and I'm sure I'd have just as much fun on a second viewing. Your age will not have much of an impact on how enjoyable you'll find Shaun the Sheep Movie. But is it a memorable movie? No, it's not. It's not up there with Aardman's best, but that's speaks more to the quality of the studio's output than a lack thereof in this specific case. It's worth watching, it's a far better animated film to take your children to than another that I could mention, and it might even be something to revisit every year or two. One bonus of not being particularly memorable is that you'll almost entirely forget it shortly after seeing it, making every viewing feel fresh. This is one you should check out. (If you paid to see Minions, see Shaun the Sheep Movie as penance and all will be forgiven.)
Bottom Line: Shaun the Sheep Movie is well-animated, funny, and extremely entertaining, even if it is a touch forgettable due to a lack of depth.
Recommendation: See Shaun the Sheep Movie if you like animated movies or comedies, or have children to whom you'd like to expose good movies.
If you want more of Matthew "Marter" Parkinson, you can follow him on the Twitter @Martertweet and check out his weekly movie podcast.