First of all you should not refer to it as "castration" - he will be neutered. Most vet's recommend around 6 or 7 months old. We will most likely have Bailey neutered this month - he's now 6 months old and has lost most of his puppy teeth. Good Luck!!
why not? It is the correct term for specific gender. Neutering is the general term for both male and female desexing(removal of reproductive organs, testicles/ovaries)
"Definition of castrate verb from the Oxford Advanced Learner's Dictionary
castrate verb
castrate somebody/something
to remove the testicles of a male animal or person
castration
noun [uncountable, countable]"
"Definition of neuter adjective from the Oxford Advanced Learner's Dictionary
neuter adjective
(grammar) (in some languages) belonging to a class of nouns, pronouns, adjectives or verbs
whose gender is not feminine or masculine
The Polish word for ‘window’ is neuter."
"Definition of spay verb from the Oxford Advanced Learner's Dictionary
spay verb
spay something (technical)
to remove the ovaries of a female animal, to prevent it from breeding
Have you had your cat spayed?"
so technically Castration is more appropriate for this topic as the question is specific to owners of male dogs as apposed to female dogs