If you watch the people exiting, you will see some with their hands down. It gets tiring, they are frightened, etc. Its any sudden moves that will get their attention. So, hold your hands up and or away from your body, so you don't stand out, you don't look like a bad guy. When asked or if required by law, then inform. I would at earliest time, but too soon and they'll march you out much more aggressively.
That is one of the issues I have with teachers carrying, 1st responders are told, "person with a gun" and they come around the corner and the teacher is carrying, looking for the bad guy. Cops see a bad guy with a gun. Proper training of a teacher or CCW person is to protect in place with students and then wait for police to respond. If in that situation, I would inform police I was there as security for the students, and I was armed.
If exiting and you have some health issues, just do what they say and move slow. If you move slow and lay down, arms outstretched you should be fine, although there have been cases that police don't respond (I am thinking of the hotel where the police officer is screaming at the guy, move, don't move, move and then they shot him... BUT, the vast majority (vast) of police will keep calm, if you are calm or as best as you can be.
Ed