I am a bit old to be worrying about the sort of family planning you might be thinking about, but I am sure a little coordination between the members of my family through the use of a shared calendar wouldn't go astray.
For as far back as I can remember, we have always had a calendar hanging on the wall in the kitchen. Occasionally someone would add an event or activity, but it was always out of date or missing key events. The other issue is that you need to be in the kitchen to see what activities are happening for the family. I am sure that an online shared calendar that all the family have access to would make a big difference.
In this digital age, how hard could it be to get everyone in the family to share details of any family activity to the family calendar? If I am going to transform my family to a shared calendar experience digitally, then adding an event, and sharing it with others, needs to be simple and quick.
The hardest part of this task is not the technology, it will be the change management. Getting the family to add an event will be a good start, and I will see how that goes. Wish me luck, and I will report back on progress.