In a bowl, stir together the vinegar and sugar until the sugar is dissolved. Fold in the strawberries, cover, and chill for at least one hour. Remove from the fridge when you're ready to start cooking.
Heat the extra virgin olive oil in a large skillet over medium heat. Sauté the shallots until softened, then add the leaves and turn until well mixed. Cook just a minute or two until all the leaves have wilted but are still fully green.
Remove greens to a strainer and keep warm.
Dry the scallops and shrimp well and sprinkle with the coarse salt. Heat a skillet or sauté pan over medium high heat until quite hot. Add the grape seed or light olive oil, let oil heat a moment, then carefully add the scallops and shrimp (there will be some spattering.)
Let the shrimp sear for about 1 minute per side until just opaque. Remove and keep warm. Don't move the scallops until you can see a brown edge forming around the bottom (about 2 to 2 1/2 minutes.) Carefully lift one scallop -- if the surface has a nice caramelized color, turn them over.
Cook for just another minute until the scallops are springy but not quite firm. Remove the scallops and keep warm.
Wipe out the pan, then add the strawberries and vinegar. Remove the strawberries after they are heated through (about 30 seconds) and let the balsamic cook down briefly until thickened to a syrupy consistency.
To serve, place the green on a plate, top with the scallops, shrimp, and strawberries, then drizzle the balsamic reduction over the scallops and shrimp.