If you're shooting from the crowd, take a P&S.
The flash will be somewhat covered by people's phone lights/flashes.
There's still a tiny chance the flash won't be well received. (I'm a concert shooter, and we're not allowed to use flash at all), but since you'll be in the midst of a bunch of people holding up their phones, you're more likely to get away with it.
Don't try stashing an extra lens somewhere, you're making security's job harder, and they won't be impressed if they have to retrieve it, and don't try to pass off a TLR as a medicine holder for the same reason.