These are easy to make and delicious. Get the kids to help in the preparation. It's a lot of fun to get all covered in red beet juice.  Make a double batch of the pickle brine and use it for other veggies such as onions, carrots, cucumbers, etc.
8 beets, about 2 pounds 
1 teaspoons celery seeds 
1 cup sugar 
4 teaspoons dry mustard 
  Salt to taste 
1 1/2 cups vinegar

Start by washing the beets and trimming the root and stem. Place in a pot, cover with water and bring to a boil. Reduce heat to medium and simmer for 50 minutes or until tender. Drain the beets, reserving 1 cup of the cooking liquid. When the beets have cooled, using your hands slip the skin off the stems. Slice the beets into 1/4-inch thick slices. Place them into bowl. Place the celery seeds in a cheese cloth and tie. Mix together the sugar, mustard, and salt together in a small bowl. In a small saucepan, combine the vinegar, beet liquid and spice bag. Bring to a boil, add sugar mixture, reduce the heat and allow to simmer for 5 minutes. Remove and discard spice bag, pour the hot liquid over the beets and allow to rest, covered, at room temperature for at least 24 hours. After refrigerate in a covered container.