I would excersise caution with this one. I took my 3, ages 5, 5, and 11 last week. I enjoyed it and one of the twins and my 11 YR old liked it.
However my 5 yr old who is usually the braver of the two did not care for it and was quite scared a few times. ( The other however asked to see it the next day)
There are several scenes.... SPOILER ahead..
A robot trying to vaporize the boys in the movie. That scared him a lot.
Then they get attacked by aliens. who kind of look very similar to the aliens in the ALIEN movie from way back. That I thought was very scary as did ds 5.
As a point of referance all 3 loved Harry Potter. and were not scared. However Zathura was another story.