How do I create a 3 year summary of family's giving history per year?
You can do this for any number of years, not just 3. In order to do this, it will require creating a pivot table in Excel (if you don't have Excel, you can modify this instructions to be used in Google Sheets).
First go to the Offering Module (1) and the Contribution List tab (2). Then select your date range (3). Click View Contributions (4) to generate the results, then Export to CSV (5) to export the data to excel.
In Excel highlight your data and choose Pivot Table from the Insert tab.
In the PivotTable Field List on the right put Posting Date under Column Labels, Names under Row Lables, and Amount under Values( it will appear as "Sum of Amount"):
To Group By Year:
Right click on your first Date (this should be in cell B4) and choose Group. Deselect Month and choose year. Then click Ok. This will display the 3 year totals for the various funds. Alternatively you can do Quarters or Months.