> because of the LEDs being low efficiency and having to be visible
> in broad daylight or whatever

You've hit the snail on the head

If LEDs are chosen that are bright enough with current that can be
sourced safely from PIC pins, that eliminates the high-side driver.
Then all you need on the low-side are simple column switches

It's the typical way 7 segment displays are driven. Anodes to PIC
pins via current-limiting resistors, commoned and strobed cathodes

A perfect example

http://www.mikroe.com/en/books/8051book/ch7/images/21.gif

The 64 x 7 LED message board of mine I linked to uses HP LEDs
(HLMP-1385, had them for over 10 years so don't know if you'd
find data on those now) that are well bright enough at only 2mA.
The description on the packet with the remaining few says 10mcd
@10mA, but I've not noticed any appreciable increase in brightness
at 10mA

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