I want to go on them BUT are they well family oriented.... How do they compare with RCCL?

Hello CRUISELOVER94,
I have not been on either line but from what I have gleaned on this site, if I was taking my whole family, I would definitely take RCCL (actually I would take Princess, but they weren't included in your question). The RCCL ships seem to have many more diverse activities and they seem geared more to families.
You also may want to read some of the reviews of Costa in the Cruise-Reviews section of this site: they are mixed at best.

It really depends on what ship and what itinerary. The Royal Caribbean ships that have more activities are the Voyager and Freedom class ships. If you are taking the Radiance class or Sovereign class then the Costa cruises would have about equal activities. If you are looking at Costa for Europe then it will be a different experience (more European passenger mix) than Costa in the Caribbean. I would suggest talking with a cruise oriented travel agent that can help you.