Many thanks for pointing the typo.
As for your second remark - I think a restaurant is an organisation rather than an object and you surely can ask a company or any other organisation to do you a favour.
Let’s see what Alan says.[YSaerTTEW443543]
Just to add something to which Torsten has already written. You are asking how one can ask a restaurant to do something rather than ask a person. As Torsten has already indicated, this is perfectly acceptable. I thought back to my schooldays (which were a long time ago) and I remembered that we did some work on figures of speech. The one I have in mind is called metonymy and it means using one word to represent another, which has happened here: the restaurant really means the manager/the receptionist/a member of staff … This figure of speech can be clearly seen in this sentence: The kettle is boiling - which really means The water is boiling.
thank you for your response. And to make myself clearer for you Alan, I have another question. In this sentence the family is allready in the restaurant ( as I have understood it ) or they just asking for a reservation and making sure that the restaurant can them provide a high chair?
You certainly do want to know what went on in that restaurant!! When I wrote the sentence, all these thoughts were not going through my mind but clearly if you want to make sure something is done then you naturally arrange this beforehand.