I had only been on two cruise lines carnival and RCCl both are great.
But for me, If I had a big family with kids, RCCL is the best option,they have a lot of family activities on the ship, surfing, golf, ect. Carnival is a more active cruise line and my favorite, but it mostly a cruise line for Party people, they have a great kids program but is mostly depends on what do you want to do. If your looking for a 7 day cruise is a nice start.
welcome to this addiction once you try a cruise vacation there is no way you will be back to the hotel options...