I'm sorry but the phrase "guys and girls" just reeks of passive systemic misogyny.

So, the guy is not some sort of male at any age, but not a boy.

A 'girl'? Umm, how is it ever acceptable to refer to a woman in a professional space as a 'girl'?

If you're trying to be all casual and still differentiate between the genders of fully grown experts in their highly technical fields? No! It is not acceptable to refer to your women colleagues as 'girls', even when referring to the men as 'guys'.