We also have kids that we take with us. I can tell you that the more storage you have the more you will take with you and still probably not have enough space.
We found that the 2 single most usefull features that we added have been the trash compactor and the extra height, that really makes the overcab bunk nice. The compactor really helped. Also pay close attention to the size of water and sewer, both need to be doubled and we actually only doubled the water and are short on grey water storage.
Patrick is right, Lonnie is the man!!!!