可以说They are easy to make mistakes不说It' easy for them to make mistakes吗？

可以说They are easy to make mistakes不说It' easy for them to make mistakes吗？

They are easy to make mistakes

句子成分不完整

they are easy to make mistakes中的easy指他们有经常犯错误的倾向

It is easy for them to make mistakes中的easy指犯错误这件事很容易

这两句侧重点不一样，就语法来说都没有错误。

They are easy to make mistakes侧重人，他们很容易犯错误。

It' easy for them to make mistakes侧重事物，这件事很容易犯错误。

你若用 they are easy to XXX 的话，有点意思不通顺。因为 easy用作形容词的时候，修饰事物是简单的，修饰人是很随和的。they are easy 就成了说他们很随和，就和后面 to make mistakes链接不上了。

用 It's easy for them会比较正确。

同时你也可以这样表达：

They (would/will) easily make mistakes. easily 也可以放最后。