Royal Carabean Cruises (RCC) offers pretty much the same expierence as most carnival corparation ships, ie. Carnival, Princess, etc. The only thing is in the long run Carnival maybe cheaper as i have heard of the purser charging for a band-aid! You made a good choice in my opinion as those ships are not MASSIVE but not to small, (Oasis is HUGE!) Consider Letting them try the teen club. Port Canaveral/ FT. Lauderdale/ Miami are the main ports. Really everything comes down to service, Rcc lacks a little but should create an over all good trip! Have Fun
TIP: lower the suggested tips as 4 people X 10 dollars = 40 dollars a day plus gas
Lower it and give some of the difference to your waiter and steward.