How to use - Saseteageru (させてあげる）
First of all, させてあげる (Saseteageru) is not a form of Keigo. It's used when the
speaker feels he/she is higher in status than the object, and used when the speaker
will "permiss/allow" the object to do something.
Some examples how to use させてあげる。
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あかちゃんに食事を食べさせてあげる。
I will allow(help) the baby eat his food.
The speaker here implies he has more power than the baby, and so will feed him.
今日は彼氏の誕生日だから、なんでもやりたいことさせてあげる。
Since it is my boyfriend's birthday today, I will allow him to do whatever he wants.
This implies although the girlfriend has power, she will allow the boyfriend
to do whatever he likes because it is his birthday.
もうしばらく考えさせてあげる。
I will give you a little more time to think about it.
Again, it implies the speaker has the right to decide whether the listener gets more time or not.
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Another similar form is させてあげて . This is like "Let" in English, and
used when you want to get permission for somebody other than yourself.
Sentenced can be constructed in the following format.
"You(or somebody), (please) let somebody do something."
For example, if you want to get approval from your father so your sister can drive a car.
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Japanese : お父さん、妹に車を運転させてあげて。
English : Father, let sister drive the car.
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You can also omit the subject and object. When you omit the subject, it's implying "you".
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Japanese: お腹いっぱい食べさせてあげて。
English: (You) let (him/her/it) eat until satisfied.
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Note, as mentioned above, させてあげる/させてあげて implies the speaker is higher in status
when compared to the listener. It can have a condescending feeling , so you should
certainly not use it with your clients.