A few characters flirt with each other.

When Mia and Tia are in front of Lightning McQueen after the first race movie, them flashing their lights resembles woman doing the breast flash which could be very difficult for young children to even understand.

Many scenes that take place at night are a bit frightening.

lightning says that racecars don't need headlights since the road is always lit, another automobile replies "so is brother but he still needs headlights", could be a drug reference.