We always book RFS for our cruises for the family. 8 of us, kids 14-27. The suite has TV's in the master bedroom and the sitting area. The bath in the master has a tub. There is a CD, DVD player in the sitting room. RFS gets access to the Concierge Lounge and you can have the menu from the main dining room delivered to the suite. There is plenty of room to stretch out and relax. You won't regret it.
The GS is large enough to handle 4. If the older child insists on not sleeping with their sib you can always bring a single aerobed and they can have their own beds. There is enough room for that. We have done this under similar circumstances