Chuckles, what a good idea to take the "kids" and make it an anniversary celebration. You'll all have a great time.
It's best to book as far ahead as possible to get the best rooms you can. Use an experienced cruise seller, who checks the price of the cruise periodically between sale and sail. Cruise lines don't call travel agents or passengers when the price goes down. You need to use an agent who will check the price and, if the price of your category of rooms goes down, will get the cruise line to adjust the price for you.
Using an experienced travel agent also will help you choose the right cruise line for you. Cruise lines, and individual ships on each line, have a "personality" and unique characteristics. A good travel agent will find out from you what your wish list is for the perfect vacation, and will steer you in the right direction to meet your needs.
Freestyle cruising refers to Norwegian Cruise Line's dining program of eating dinner when and where you want, if you don't want to sign up for "Main" or "Late" seating for the whole cruise. All cruise lines have now adopted that system, so you have a lot of dining options on whatever cruise line you choose.
The best area of the ship again depends on your preferences and budget. There are rooms with no window, rooms with a window, rooms with a balcony, and suites. Your travel agent will explain the differences among these room types. I suspect your agent will suggest one room for you two, and a separate, perhaps nearby room for your sons.
The earlier you book, the best chance you'll have to choose the types of rooms you want in the locations you want.