介词to 和of的用法

你好。在你的句子里，to 和for 都是对的。又如：
Sit down for a rest (修饰名词rest)
Sit down to chat with me (修饰动词chat)
Sit down to a cup of tea.(修饰名词a cup)
We sat down to dinner at six (修饰名词dinner)

We sat down to dinner at six.
句中的to 不能换成 for

Sit down to 坐下来从事，这是固定搭配
sit down to dinner坐下吃晚饭

没有sit down for的搭配

二楼说得对。 sit down to .... 专门指“坐下来准备做某事”之意。英语解释是：to sit down at a table to do something, such as eat a meal or attend to some business. 比如就餐，开会，谈判等等。比如：（1）At six we all sat down to dinner. （2）Ted looked forward to sitting down to a big Thanksgiving dinner. 需要注意，to 是介词，后面只能带名词性的结构，不是动词不定式里的 to。sit down to a meal 和 sit down to eat 是不一样的。

我觉得用for更好一些！