Anybody know how best to handle this?

I've got a challenge, and I'm wondering if anybody can offer possible solutions. I run a membership program, and I want to turn one Android device (7" tablet) into a key pad for members to enter their ID, while a second Android tablet (facing the staff behind the counter) brings up the member info associated with the entered ID. They can then perform specific transactions in the app for that member. The user experience needs to be very different for the member versus the staff, because we do not want the members to see what my staff sees. The member should only see this as a key pad, perhaps with some type of personalized messaging while the staff performs transactions.

Do we need to build two separate apps that send and push info back and forth from the server, or can this be done using one app? Also, would it make sense to connect the devices using bluetooth, or does it make more sense to send data to the server and back over wi-fi?

It's probably obvious at this point, but I am not a developer. I'm just trying to get suggestions for how best this can be done so I can speak somewhat intelligently about it when I do approach a developer.

I'd appreciate any suggestions. Thanks.

Eric