The sentence you wrote is almost correct! Here's the sentence:
"Daddy penguins keep the egg warm on their feet while the mum goes to find food."
It's mostly good, but to make it clearer and grammatically perfect, you could say:
"Daddy penguins keep the eggs warm on their feet while the mom goes to find food."
Here's why:
- Eggs (plural): Penguins usually have more than one egg, so "eggs" is often used.
- Mom: "Mom" is more common in American English for children, but "mum" is British English and also correct.
- Overall: The sentence is understandable and good for an 8-year-old!