By "if its really 90mA per display then a 1000uF might help a little" seemed to me that you meant 1000uF per display.

In any case though, the 1084 or even the humble 7805, do not have any problem with large capacitance.

I bet a reverse biased diode, across output/input pin, would be needed to protect the regulator, in case the Reg. input is grounded for whatever reason while the outuput cap is still charged.

Ioannis