Michelle have you got a copy of your daughter's ACTH results? If not - get them, because by obtaining your own copies of the results
1). You will quickly learn the names of all the things they test for.
2). You will see what the normal levels should be as opposed to what your daughters levels actually are.
3). You'll see for yourself when your daughters levels are askew, as doctors tend to often say "oh everything's ok".
Learn as much as you can about LOCAH so that you can be your daughter's advocate.....and as for the statement by the doctor "don't worry" well of course you will worry. However by learning as much as you can you will have a much better understanding of this condition and some sense of control.
If you want you can post her ACTH levels here, as we often get a very good idea of severity based on the levels.
Also yes your son should be tested in the near future as he is obviously younger than your daughter and may well not have exhibited symptoms yet. Let things settle down a bit first with your daughter and when you feel ready go for it.