If you have access to laptop computers, cell phones, etc. then you can use those to pass messages which the others can't see. As a matter of fact with computers you can prepare even complicated messages to send. You can also use the old fashioned way if you have information that doesn't need huge amounts of conversation to convey, just write or pass notes.
Also if some of you speak another language, like Greek or Latin or Spanish or German then just use that language. Of course then those people have to correspond to the characters who need to use a different game language. Since our setting is the Byzantine Empire several of my players peak Greek or Latin, which makes for fun situations where they are told something in Greek or Latin, and then the players have to translate and one player or another will disagree with a translation. That's fun to watch, but it may not be practical in your situation. But when I was young we always just passed notes to keep information confidential. So good luck.
And like JB said, welcome aboard.
