For 2 adults and an 11 y/o...1 larger suitcase, 2 smaller pilots type get checked. Then my dd and I each have a totebag that we use for carryon. In those we have clean undies, bathing suits, water, meds, passes/confirm. numbers, cash. Dh usually carries the camera case. But, we may be able to do away with the larger case and do 3 pilots suitcases in June since we won't be bringing any food this time.
The thing we try to do is to pack a little for each person in each bag. That way, if one gets 'misplaced' someone doesn't lose all their stuff in that one bag.