In a large bowl, toss shrimp in Old Bay Seasoning until well-coated. Preheat your grill to 350-450 degrees, and cook the shrimp over medium direct heat for five to seven minutes.
For the slaw, in a small bowl, mix together buttermilk, mayonnaise, dijon mustard, apple cider vinegar, sugar, lemon zest, and juice.
Add the cabbage and carrots to a large bowl. Pour wet mixture over the cabbage and carrots, then toss to mix all of the ingredients together.
Put slaw into the refrigerator to chill.
Next, make your Chipotle Ranch Sauce. Add all of the ingredients to your blender, and blend well.
To assemble your tacos, start by adding a tablespoon of the chipotle ranch sauce to the middle of your tortilla. Add ⅙ of the cooked shrimp. Top with slaw-- as much as desired, then top with a drizzle of chipotle ranch sauce.
Finish by sprinkling a few green onions on top. Serve immediately.