问题提得很有水平。

1. 句子用了将来时态，把wearing that mask 看作条件状语更好一些。

You’ll frighten the children wearing that mask. 你如果戴那个面具会吓着孩子们的。

可理解为：You’ll frighten the children if you wear that mask.

2. 句子用了完成时态或过去时态，把wearing that mask 看作方式状语更好一些。

You frightened the children wearing that mask. 你戴着那个面具把孩子们吓着了。

可理解为：You frightened the children by wearing that mask.