Gerunds are a headache for anyone Yun. No one really knows where the English language is going with them, for all the confident talk. They can be nouns that take subjects and objects and assign case!!
There are two types: Nominal and verbal.
There are three verbal types: Accusative -ing, Possesive -ing, and PRO-ing.
If anyone tells you A) or B) is wrong, without an explanation, it is because they don't know and are guessing. A) is awkward, but not wrong.
Was it you who asked about 'I want the photos for sending to my sister'?
This is a quote from a paper by Robert Malouf, summarizing the properties of gerunds.
(13) a. A verbal gerund takes the same complements as the verb from
which it is derived.
b. Verbal gerunds are modifed by adverbs and not by adjectives.
c. The entire verbal gerund phrase has the external distribution of an
d. The subject of the gerund is optional and, if present, can be either
a genitive or an accusative NP.
The properties in (13) are shared by accusative subject (acc
-ing ), genitive subject (poss-ing ), and subjectless (pro
-ing ) verbal gerund phrases and are not shared by any other English constructions. The three types of verbal gerunds seem to be subtypes of a single common construction type, and any analysis of verbal gerunds ought to be able account for their similarities in a systematic way.
If you ever find a good explanation for the properties of gerunds, please let me know!