Your sentence is almost correct but could be made clearer and safer sounding for a 5-year-old. Here's the sentence you wrote:
"I skip on steep cliffs and enjoy the heights."
Grammatically, it's correct, but talking about cliffs might sound dangerous for a young child. Also, "enjoy the heights" is a bit formal.
A simpler and safer way to say this could be:
- "I like to skip on hills and look at the view from up high."
- "I love to skip in the mountains and enjoy being up high."
If you want to keep the original sentence structure but make it a little easier to understand, you could say:
"I skip on the steep hills and enjoy being up high."
So, to sum up: Your grammar is good, but choosing safe and easy words is important for young children.