We have NEVER given our 7 year old SWCAH daughter salt supplements, nor have we salted her food.  She will have salt on hot chips, like the rest of us, but I do not salt any of her other food and she has NEVER craved salt.   I do believe, however, that there are varying degrees of salt-wasting/losing, so each child may be different.  Our daughter certainly doesn’t seem to need or want the extra salt, has never asked for salt (she has even complained that something tasted too salty!) and I am reluctant to give her too much salt as it may interfere with the florinef she is taking and she my also become used to the salt taste and need it just for the taste.  You would be surprised how much salt is actually in everyday foods that we eat!