I don't think the white vinegar will hurt...apple cider vinegar has more beneficial properties than white vinegar (certain compounds from the apples) that are good for hair, but I say if the white vinegar's working, go with it!
As for someone's suggestion to use Dr. Bronners on hair, I would dissagree...Using an alkaline cleaner like that will actually damage hair. The high pH will actually lift the cuticle of the hair, making it more prone to breakage and damage.
If he hates the vinegar routine, and you still want to no-poo him, you could always use a soapwort shampoo. Just make a tea with a blend of soapwort root, nettles, yucca root, and add some essential oils for scent, and you've got an all-natural shampoo. No baking soda or vinegar needed! Pour it on gradually, massage the scalp and rinse well!