Multiple discrete keyboard inputs on one machine

Multiple discrete keyboard inputs on one machine

Background:
I am running a large event in October and plan to monitor who attends and
where people are in the building for safety using a system that reads
mifare cards that everyone in my organsiation has. To do this I have found
a cheap mifare reader that reads a particular sector of the card and
returns the data as hex which I can convert to a string then send to a
server for processing and recording. So far, so good. However, close to
20,000 people attend this event and that means a lot of scanning and so a
lot of mifare readers, all of which need to be connected to a computer to
read the data and send it on. Ideally, I'd like to connect about 3 or four
readers to a machine, and have about three or four of these, one on each
entrances/exit at the event.
What I need help doing:
My card readers act as generic keyboards on Windows and Android (and I
assume Linux, but I'm about to check this), the computer in essence just
acts as though it has multiple keyboards, all of which can enter data
simultaneously, but only to one program (i.e., there's ever one caret on
the screen). This could cause a problem if two cards are scanned at the
same time and the keystrokes from each card get "intermingled" and so
cause processing problems.
What I'd like to do is set up one linux box to have multiple carets, so
that I could have say four command lines all going at the same time taking
data from one card reader each.
For example: if John and Saira scanned in at the same time, at the moment
the resulting input could be:
j s o a h i n r a
Whereas I'd like it to be:
CLI 1:
john
CLI2:
saira
etc. etc. for CLI3, CLI4
I know this must be possible, I'd looked at potentially settign up a
multi-seat linux distribution, but I feel that would be using a
sledgehammer to solve the problem, and creates a new problem since it
introduces the need for monitors, mice, etc.
Ideally I'd like this whole system to be as streamlined as possible,
either running off a laptop or just a linux box that I can plug in, boot
up and let run automatically (with no need for monitors, mice or other
clunky bits and pieces!).
Does anyone have any experience on this or advice they can offer? Any help
would be much appreciated!
Thanks,
Dom