At the core of family vacations are fun things to do
. Most of which should be free. Of course, some things are going to cost you. During the course of the vacation planning process, make a list of activities that you absolutely must do. Research those in advance. Have a backup plan of things to do in the event of inclement weather.
Putting time, effort and some resources into planning your family vacation will make for a better experience. Having a trip plan, daily itinerary and activity schedule is not going overboard - it is vacation planning.