不定式的地方问题

儿子没吃早饭，爸爸给儿子早餐费，让他自己到学校后在学校饭店买点早餐吃。下面两个句子是不是能表示这个意思？

To buy and have some food, he give his son some money.

He give his son some money to buy and have some food.

这两个句子意思一样？不定式的逻辑主语是不是一样？都是son?

推而广之，大家在阅读中判断一个不定式的逻辑主语时，需要注意不定式的地方，不定式的逻辑主语和不定式的地方有关？

To buy and have some food, he give his son some money. 错误

He give his son some money to buy and have some food. 正确

不定式短语为与宾语有关的目的状语，即不定式的逻辑主语为句子的宾语，此时不定式不能置于句首。句首的不定式的逻辑主语为句子的主语。