Absolutely nothing. Just some hugging between characters. This is a children's animated film anyway.

Aunt Dete briefly mentions Heidi about her parents having passed away.

Dete and a grandfather have a serious argue about where Heidi's gonna live. Here, Dete briefly grabs Heidi's arm, but nothing serious happens.

Peter pushes Clara's wheelchair down a mountain road, causing it to crash into a rock and get destroyed.

Nothing bad. Peter says "gee" once. The grandfather mentions about "people being foolish" during a conversation about a bird.

None.

There is a scene where a little goat is about to fall from a cliff, but is saved by Heidi and Peter. Beside from this scene, there is nothing to worry about since this animated film is perfect to be watched by a whole family.