Two Days Ahead: Do the shopping and buy the rosé. Make the tapenade.
One Day Ahead: Blanch the haricots verts and the Dijon vinaigrette; store them separately in the refrigerator. Make the crème fraiche dip and chill. Make the quinoa salad and chill. Make the financier batter.
Day of the Picnic: Make sure the rosé is chilled. Bake the financiers (they taste best the day they are baked!). Toss the green beans with the vinaigrette. Assemble the sandwich one to two hours in advance; press and wrap tightly. Pack your picnic basket and cooler, grab blankets, and head to the park!