Well, uncanny dodge requires an attacker to hit you, so doesn't work with an breath weapon. Using anything with the name weapon as intended as action in combat is clearly an attack, so your invisibility is gone. Precisely the result which feels logical, so end of discussion at my table.
And no there is no question whether using a weapon in its intended way is an attack. Otherwise they could have simply stated the rule 'you're making an attack if and only if you're making an attack roll. They didn't, so there must be cases where something clearly counts as an attack without requiring an attack roll.
And no there is no question whether using a weapon in its intended way is an attack. Otherwise they could have simply stated the rule 'you're making an attack if and only if you're making an attack roll. They didn't, so there must be cases where something clearly counts as an attack without requiring an attack roll.