amadeo-child-of-the-renaissance:

//I imagine that Daniel had to struggle with the rest of the coven for some time, until they got used to his presence.

I think that Lestat, Louis and Armand would probably have talked to each other in French all the time, whilst Armand would switch automatically back to (ancien venetian) Italian whenever he spoke with Marius.
Just out of habit! They have, after all, spoken with one another in the respective language for centuries.

So, there was Daniel, who probably couldn’t speak French to safe his immortal life and had to constantly remind them that it is rude not to let him in on conversations.
By now they all got used to talk in English constantly.

And Daniel has gained some skills in French, at least according to Armand…