To begin with, cut your worms in half to make smaller and lighter worms. I believe this also helps them absorb the vinegar better as well.

Fill a jar or glass with warm tap water, stir in baking soda well then put in your worms.

Place vinegar in another glass and set aside.

Now go find something else fun to do for 15 minutes while you wait for the next step, you can let the kids experiment (play) with a pile of baking soda and a dropper with vinegar.

After 15 minutes, have your child drop 2-3 worms in the glass of vinegar that you set aside earlier. At first, bubbles begin to form then slowly the worms will start to wiggle slightly and rise up in the cup.