I am an adult with three kids, and I loved this movie! My girls (ages 9, 5, and 1) all loved this movie, too!
The story is a great one, and I was tied down the whole movie. It's not like many kids movies -- that make adults laugh -- it's a great one that isn't just a kid's movie. The acting was amazing, and that's pretty rare with movies like this. Ysa Penarejo (Toulane) was by far the best actress, but everybody else was great, too. Cathy Rigby is also a main character in this, so that was pretty exciting.
The only slightly funny (and awkawrd) thing was the one "broken friendship" scene with McKenna and Josie. The whole scene was fine, but the broken romance song (clearly the only song they could find) made it look weird and not just friendship. However, it all ended up great.
There is nothing bad in this movie whatsoever (no drugs, I promise) and it has great messages and all that good stuff. It's truly an amazing movie, and you should definitely not only let your kids watch it, but watch it yourself.