We did this on the Spirit. We had 22 people in our party. Two of the familys had gotten suites and when we got to the checkin point they took us all to the VIP check in spot. So, when you get to the terminal, go to the VIP check in area and tell them your "childern" are traveling with you and I'm most certain they will take care of the whole group.
It really doesn't make that much of a difference as far as we could tell. It seemed like all it bought us was a "go directly to go" pass to the check in counter and we had arrived early enough that the wait wouldn't have been that long any way. But.. it is still nice to have the VIP check-in. It makes you feel special.
Carnival Cruise Lines:
Fantasy 90, Celebration 95, Victory 05, Conquest 05, Spirit 6/06, Freedom 6/08, Holiday 7/08, Victory 6/09, Valor 9/09, Dream 6/10, Splendor 8/10,Conquest 8/11,Magic 11/11,Triumph 4/12,Spirit 7/12,Freedom 11/12, Triumph 2/13 - The fire cruise
NCL Dream October 2006, RCCL Mariner OTS June 2007, Celebrity Silhouette 2013