OK, specifically which yeast do you have? EC-1118, DV10, Pasteur Champagne, Pasteur Premier Cuvee?
It makes a difference which champagne yeast you use, and how you feed it nutrients. Any of the Pris de Mousse yeasts will throw heavy amounts of sulfite when improperly managed in primary fermentation. They will produce up to 50 ppm of sulfite which is equivalent to 1/4 teaspoon in a five gallon batch, which incidentally is the recommended dosage for a sulfite addition. If you have friends that are "allergic" to sulfites then I would recommend that you steer them away from any mead you make with EC-1118 and Pasteur Premier Cuvee if you do not follow a diligent schedule of nutrient dosing because it's possible to end up with a mead that has as much sulfite as if you added 1/4 tsp to your batch.
That being said, other champagne yeasts like DV10 do not produce the amounts that the Pris de Mousse yeasts will, and can be used for lees aging as well which in my opinion really helps to add complexity. If you want to get really daring, you can encourage some Brett activity and follow with some MF if you're feeling really over the top.
Hope that helps,
Oskaar