Two resourceful moms have built a website dedicated to getting your kids off the couch. It is called appropriately, KidsOffTheCouch.com. Each week they feature a memorable movie for the family to watch together and couple it with an off-couch activity.
Some of their garden related activities include:
1) The Secret Garden + Edible Gardens
2) My Fair Lady + A Flower Market Visit
3) FernGully: The Last Rainforest + Botanical Gardens
Lastly, as a bonus, the illustrations by Laura Cornell are brilliant.