Congrats on becoming Platinum!
Yes, the official rule is they need to share the same Sail & Sign account, or if there is another cabin on the booking with minor children.
I've actually had cruise friends go through the line at Tampa quicker than I went through VIP check-in. I still was taken on the ship first though. As Dave mentioned it will depend on the strictness of the check-in agent. I've also seen them go get non VIP cards for people a few times.