Two things to be aware of with that amp:
The 2µ/C offset is typical, not maximum. If you need a guaranteed maximum limit, then you must buy an amp with such a limit stated.
The input bias and offset currents must also be considered. These translate into voltage offsets when multiplied by the equivalent resistance at the plus and minus op amp inputs.
And the variation of the gain resistors with temperature must be determined. A typical 1% resistor may have 50ppm/C change which can translate into significant voltage changes, as determined by the gain changes this causes and the voltage output of the amp. You may need to consider using high stability resistors (such as 0.1% units). Also consider the stability of the trim pot.
Unless the circuit resistances are above a megohm, you shouldn't have to worry about guarding the summing junction or any other unusual layout considerations. Just good normal layout with adequate decoupling capacitors to a ground plane, and short trace lengths, especially to the summing junction.