Well that is not going to be very bright due to the 8 to 1 multiplexing going on.
Read about multiplexing here:-
http://www.thebox.myzen.co.uk/Workshop/LED_Matrix.html
Using a TLC to multiplex means you are going to have to synchronise your reading of the buttons with the multiplexing. This means hacking into the multiplexing library to read all those inputs when ever one of the P-channel FETs is turned on.
Not an easy task for a beginner. I would go and kick the person who designed that hardware.
However it is very close to my project:-
http://www.thebox.myzen.co.uk/Hardware/Econo_Monome.html
and
http://www.thebox.myzen.co.uk/Hardware/Hexome.html
But I suspect the TLC driving library is different to that which I used.