sorry to hear you are in so much pain. is it possible to slip in a hot tub w/ some Epsom Salts before you head out to your family function? maybe that would ease it a bit. or use a wet towel heated in the microwave & place on your lower ab ... i sometimes have bad cramps - but not each month like you describe - but when they bad oh man it's just awful so i feel for you.
as far as the SWF (Salt-Water-Flush) some people substitute the lax tea in the am. find what ever you are comfortable with so long as your bowels keep moving. personally i like the idea of the liter of h2o to help flush things. you could also alternate days as a compromise.