All of the kids and parents saw this today, and the kids liked it a lot. It had a decent story line, and was the first movie my 5-year-old watched, followed, and didn't get bored of partway through.
That said, it just wasn't very funny. Pleasant, but not funny. Normally, my kids giggle and laugh through movies like this (they thought Alvin & the Chipmunks was a laugh riot), but my 8-year old only laughed once. I laughed about 6 times...but really, if you can count your number of laughs, that's a bad sign.
Overall, the characters were nice - and there wasn't anything we had to explain or contradict afterward. Very very little violence and nearly no scary parts (about 3 intense minutes near the end, and one slightly creepy character morph). My husband was thrilled that there was no love interest.
Our other thumbs up is that the characters all act pretty realistically - they talk to each other, and there's very little lying or contrived Three's Company-style situations.
It was a fun little movie - I just wish it had been funnier. Oh, and stay through the credits. There's a little bit at the end.