First, who in their right mind is going to give a rat's ass what critics would think about a TMNT movie? Especially after this summer, the critics are pretty much worthless when it comes to movies for the GA.
Second, in this day and age of overly protective parents, I expect this movie to be no less than PG-13 because of the weapons alone. I think this movie is striving to appeal to a wide variety of people.
Out of curiousity, I remember something when the TMNT were big back in the day, and when the property started to make it's stamp overseas, there was a market that banned anything ninja, so they had to change the ninja out of Teenage Mutant Ninja Turtles, and they had to ban the use of Mikey using his nunchucks. They still do that to this day?