I took my 3.5 and 5.5 year olds to see Rango. I was not happy. (I was visiting my sister and she wanted to see it with her kids, so I went along reluctantly)
The movie said swear words (or what i consider swear words) that I did not want my children hearing. One of them being damn and now my 3 year old is going around saying the word sometimes, not sure if that is related to the movie. At one point in the movie someone said son of a b..... but didn't actually say the b word out right, but faded away as they were falling or something.
The movie talked about prostates and lesbians. Neither of which I wanted to subject my young ones to.
I tell everyone I know, that if they have young kids not to go to the movie.
Can't say anything about the Mars one, because I haven't seen it.