The idea of beings created to serve humans is not a new concept, I believe there is mention of it all the main religions about the 4 main angels created to serve humans for example Gabriel ehe angel of death, etc...

and then there are angels created to be as "guardian angels" appointed to serve individuals.

The mentioned Houri is just another unearthly being for the same purpose of guidance and to serve.

But as for the infants which I don't believe will appear infants in Heaven as there is mention that every human will be resurrected to appear at the same youthful age and free of defect or illness, I also dont believe any person who is deserving enough to go to heaven will be comfortable of being served by these boys, I'd much rather serve them rather than be served and I would make sure they were happy rather than to use them as objects and I believe this why such a concept may exist because those truly deserving of heaven would act responsibly