True, her being a succubus and being very sexual by nature does hint about it. But the beast person is an alpha and switch to a pet, the goblin is an innocent evil warlock and turns into a loving slut who even thinks of apologising to the village inhabitants, and even Ruby changes in that she doesn't try to feed on souls anymore. The change could have applied to her slut nature too though, so it's not obvious she plans to fuck around, all the more after the main character kind of did forbid her to.
What guys want mostly depends on the individual guy we're talking about. Much like with women the interrests are varied and quite often opposite from an individual to another. Spitroasting is a fairly common search word in porn. Some will enjoy the sharing scene, others won't. Given that it's just a bonus and in no way an important part of the story i would give a word of warning so those not into it wouldn't watch it.
I would just replace the special button by "special : sharing" or something once it is unlocked. But it is just my opinion as a user, it doesn't amount to much.