As far as the level shifter goes, I have an idea for a simple little hack that looks easier+ cheaper than adding one... The logshield has one unused level shifter, however the pads are being used as cheap vias in the board layout so you can't just solder to the legs in the board. BUT... if you bend the legs up when assembling so they dont go into the holes they are free to use! From this datasheet: http://www.ti.com/lit/ds/symlink/sn74ahc125.pdf, the pins in question are 11,12,13 or 4Y,4A,and 4!OE. Then you can just solder straight to those instead of adding the extra level shifter!
I don't have the hardware but let me know if it works, and let me know if I can help in any other way.