Is there a way to remove scratches from a MacBook Air lid without risking further damage?

Ellie,

Apple do not recommend anything other than the basic treatment per this document.

How to clean your Apple products - Apple Support

If the scratches are unsightly and disturb you, a fitted case would be the answer and also protect against further damage.

Ellie,

If you go to Amazon and type 'MacBook Air protection cases', you will see several offers.

In the UK, John Lewis are a respected source.