They won't separate you if you are traveling together. In fact, if you are in the same cabin and using the same onboard account you should be on the same Set Sail pass, so actually they can't separate you because you have to check in together. But even if you have separate Set Sail passes, they'll let you stay together. Happens all the time.
And Mike is correct that oftentimes the regular line moves faster than the special lanes for C&A members and suites.
One important thing to note about the Liberty Of The Seas and debarkation day. The terminal used at Port Everglades has been a pain for the past couple of years when it comes to leaving the ship. Nobody can pinpoint it but everything seems slower than it ought to be. The layout creates a walk from the ship (on the pier) to get inside and then you have the baggage and Customs drills to play. Depending on which day your cruise ends, Customs can be shorthanded. I say all of this to make one point - do not book early flights home. I would not consider anything before noon, just to be safe.