kimjovi - the best advise is to use a travel agent. You need to act on it now, if you want to sail this year, holiday time is very popular for cruising, and you could also have a hard time finding air (if needed)
Sail on a large ship- more to do.
You mentioned "Freestyle" dining - that is NCL, but Princess offers something very similar in their "Anytime Dining"
Royal Caribbean is a very family friendly line but they do not offer the flexible dining options unless you choose the alternative surcharge restaurants.