Is Teenage Mutant Ninja Turtles Season 6 suitable for viewing by a 4 and 5 year old?

I have two boys and am fairly particular about what, and how much, they watch on TV. My mom got them the DVD Teenage Mutant Ninja Turtles Season 6, and I would like to know if this is a dvd that is safe to show them or if it is better suited to older children. I'm worried about language (even mild swear words aren't ok in our house, and I'm not even that fond of the word stupid or shut up), violence, and disrespectful behavior. The DVD is rated NR, which doesn't help me at all. Please advise. Thanks!