Can't suggest any texts, I'm afraid, but I will say don't worry about the pronunciation. I see it's an Italian choir, so I wouldn't be surprised if they sing it Italianate anyway, and even if they do go for the classicists' "New Pronunciation" it's entirely interchangeable for singing purposes, just like Byrd, Tallis, Fauré &c. didn't set Italianate but work fine when sung that way.