What complicates your question and makes it simple at the same time is that you're asking about translation. As a translator, it's not your call to improve the text. Hands off.
A translator's task is to reproduce the existing text in the target language as close as possible to the original in terms of meaning, style, connotations. An over-the-top metaphor for an over-the-top metaphor, clinical for clinical, derogatory for derogatory. If the author is writing about a lily in full bloom misty with morning dew, you also translate it as "lily in full bloom misty with morning dew" (you're allowed to roll your eyes as you type). If the text on the page in no uncertain terms says vulva, you go ahead and write "vulva". If the story is talking about a cunt, you dutifully type "cunt". If you're not comfortable with that, you've chosen the wrong piece of writing to work with.
You can only edit as you translate if you have the author's consent to do so - such as if the writing you're translating is your own. Otherwise you're misrepresenting what the author said, and that's a no-no.
Considering there's a good chance the story you're translating is actually yours, and for the sake of others who are writing an original version of their story, this is what to do if you're the writer:
Presumably you're writing the scene from the point of view of one of the characters. (Honestly I can't imagine erotica written from an objective POV not crossing into the realm of base porn.)
So ask yourself, What would the protagonist call it?
If they'd think of it as a bulging rod, call it a bulging rod. If they'd think of it as a manhood, call it a manhood. If they'd think of it as a dick, call it a dick.
Being lowbrow won't really hurt the quality of the text in itself; being out of character will. Especially in an erotic scene, which is a very intimate moment for your character, staying true to the character's nature is key. A very emotional character using clinical terms, a very straightforward character using flowery terms, or a very "clean" character using vulgar terms are all equally a mismatch.
You can even use the vocabulary as a tool to show things. For instance, choosing somewhat more poetic language about the partner's body and casual about their own can help you show that the protagonist is giving attention to the partner, rather than their own pleasure.
And one more remark: A lot of erotica writers are way too flowery. The result is an unintentional parody. If what you quote in the question is representative, you too are steering a bit too much in this direction. Try to tone it down. Don't be afraid to be direct - if you want to give lots of physical detail (mind you, you don't have to, and sometimes it's better if you don't), combining such detail with a cautious taboo about the words for it is a writing disaster. And in the end it can sound even dirtier because what's fine wouldn't be unspeakable, would it?
"Breasts" has a wide range of usage, fitting for both clinical talk and casual conversation, and usually is a good option; "bosom" is more bookish; "boobs", on the other hand, is very informal (something a teenager would be in character to say); "tits" is kind of vulgar and will only really work with a limited type of protagonist; but "mounds" is something straight out of purple prose (and also, "mound" is a common euphemism for a different part of a woman's body - clitoris) - if I may be so bold, it sounds ridiculous and like the heroine is an avid reader of bad erotica, which is probably not the intended characterisation.