Donna,
We have done several cruises as a three generational group - ages 75 to 5. Oddly enough all on lux cruise lines which really are great for a smaller child. If we meet up at breakfast or lunch time fine but unless it's related to going on shore we don't plan it. It works out to 4 family units more or less, and we do meet up for dinner each night - other than one "date night" for each of the younger family units just in case they want a romantic non-family evening. We don't all take the same shore excursions though we try to ensure someone always goes with Dad as a courtesy. When we do shore excursions together we look at the oldest and youngest and plan accordingly for rest breaks and non structured play breaks. Now that Pierce is older we are going to look for cruises with children's programs which will take us out of the luxury market, but we'll look to travel in suites that provide similar amenities and pick smaller ships. Alaska and the Caribbean are the easiest - looking for bears and running on beaches are always winners! Don't know if this helps - but we've done 5 as the larger group. Oh - and with small children you can always get protective glass or netting for the balcony - a little peace of mind