Anything wrong with this level shift and amplify op amp circuit?
I would prefer to shift the voltage with a parallel power supply. Something that resembles a zener, a shunt voltage reference. Look at something like this: http://www.ti.com/lit/ds/symlink/lm4040-n-q1.pdf

This would provide a very stable 2.5v reference. That means you don't need R1, R2 R3 and R4, eliminating errors and variance. 

But anyway. If you're just trying to measure a shunt your best bet is to use an IC designed for that and you can save money and time. Take a look at this, and search for one that is better suited:
http://www.ti.com/lit/ds/symlink/ina180.pdf

http://www.ti.com/lit/ds/symlink/ina301.pdf

Specially the INA180 will already give you an output at half the supply voltage. You just need to connect both inputs at your measuring resistor and you're done. Errors due to offset voltage and current will be reduced with the specifically-designed IC.

Hope it helps