I have never read the book, which this movie is based upon, so I have no point-of-reference for comparison.
All in all I thought this movie was perfectly appropriate for families, although from reading reviewers comments on another website, you'd think 'The Last Mimzy' had some kind of subversive plot. One parent said it was 'liberal doctrine' and another focused on the fact that it shows people who actually believe in Eastern philosophies and practices. Wow! You mean there are other religions besides Christianity out there?! Then they must be liberal in nature and are trying to wreak havoc on the traditional, family-values we all hold so dear.
I am a Christian and had absolutely no problems with the ideas proposed by other points-of-view. Maybe you might have to walk out of the theater with some explanations of how other cultures see the world and their place in it, but that's part of the magic of this movie. 'The Last Mimzy' was by no means 'liberal doctrine' unless you think showing a different perspective as a threat.
Personally, the weakest parts of the movie for me was the uneven direction and the point where I asked "Why is Michael Clark Duncan in this film?" He didn't really add much to it. The kids were believable and Timothy Hutton did a decent job. The effects were all-in-all low-key, but necessary. Before you judge this film for showing the mysteries of Eastern beliefs, try watching it with an open mind. It didn't give me the same vibe as 'E.T.' or 'Close Encounters', but it did a good job as being an entertaining family film.