hi jessica! this is just my opinion, so here it goes. i have 2 non affected girls and my 3rd has swcah. i had HIM tested b/c there was question about the diagnosis. a very long story as to why. anyway, he does have swcah and i know where the defect is. it is 21 hydroxylase as well. obviously me and my husband are carriers. now, each girl that i have has a 50% chance of being a carrier and a 25% of not being one. as martha pointed out, the gene usually "runs true" meaning it would be HIGHLY unlikely that they would develop LOCAH b/c that is not the gene we have passed on. as far as dna testing goes in your case it would depend on these issues if i were you:

do i want more children and am i confident that my child has the right diagnosis? we were done having kids, so if my son did not have some questions about the validity of the diagnosis, i would not have done any dna testing.  i expect my girls to have their husbands, when they get married, tested. if their husbands are not carriers, i dont think it really matters if they are.  or they can get tested if they want to.  i think if i we didnt feel like our family was complete and i wanted more children, then i might get me and my husband tested. just so we were sure. anyway, i dont think there is anything wrong with not getting dna testing when the diagnosis is clear and the child is doing well with treatment, etc.

louise