Is having adjoining cabins a must? In my experience, there really aren't that many on any given ship and they fill up extremely quickly, so unless you book really early, you won't find any that are reasonable.
My family (myself, wife and three children) have sailed together many times with numerous room combinations and have never had adjoining staterooms because they were never available. You can, however usually find the right number of staterooms within a few feet of each other.
Anyway, good luck!