What are all the hardware (camera) and software requirements for big screen augmented reality? Is there any workaround to use Vuforia and smartphone to display on a large LED screen?
android camera - Large venue augmented reality
Basically, it will work if the target is big enough and the mobile device camera is good enough. But it will be very difficult for you to get exact answers I think - you need to test it or simulate it.
Regarding if people hide the target - again, you need to figure out yourself what the scenario is and how bad can it be. If it's very crowded and people are hiding the target constantly, using only target-based solution is not enough. If you're only talking about hiding here and there, you can use Vuforia's Extended Tracking for that.