If you dont know anything about TMNT, the movie is just OK. My 5 & 8 yr old kids liked it. As a TMNT movie (for a old fan), the movie is bad. Rotten Tomatoes was wrong.
1. It completely changes the original story. This will make old fans shake their heads all along the way. Splinter is an American rat voiced by Jackie Chan (Chinese, not Japanese). He learns martial arts by video. He is "Dad", never Master or Splinter. The bad guys are all good, and some of them changed genders. April is black. Just make a new character, don't change old ones.
2. The comedy is pop-culture reference (will go over your kids heads) & gross out jokes. You might chuckle a couple of times.