[NinjaCrab]

I have a question regarding the difference between ために and に in ~てくれる/~てあげる sentences.

In Genki II, it says in a footnote that "If the main verb does not have a place for the person, use ために. 掃除する is one such verb". けんさんが私のために部屋を掃除してくれました。

However, In my grammar dictionary it says that you only use ために with intransitive verbs. They provide the following example:

みんなは私のために働いてくれた。

This confuses me since 掃除する acts as a transitive verb in the above example. Would it be wrong to say:

けんさんが私に部屋を掃除してくれました。?

Thanks in advance.