If you're allowed to be on your own property during curfew (which I think you are from what I have read about it) then they've done nothing wrong for being outside on their porch. If the police (authority or whatever) ask me to do something and I am not breaking the law then I do not have to comply with them and should most definitely not be shot.
Legally you may be correct, like you I also don't know.
In the real world, I'd move from my porch to inside my house, even if it meant the video footage I was trying to get was not as good.