Love this idea! Shannon from Find Joy in the Journey shares this wonderful gift of 12 date nights.
For Christmas, she planned out 12 dates for her and her husband. Mostly things that are free or inexpensive and most dates are activities they've never done. She put one in each envelope. At the beginning of the month, they open the envelope and schedule the date around their current schedules.
Inside the envelope is a description of the date and additional items like tickets or a gift card, etc.
If you start planning now, you could easily have this done and ready to give this Christmas. Plus, it spreads the expense out over time if you are purchasing tickets/gift cards.
This idea would also be nice in a family or child version. Fill each envelope with a family activity, document each activity through photos and make a nice SmileBooks photo book to document the year!