Increase both R1 and R2, by a factor of 10.
Can't you reduce the current to 250μA and eliminate R1 and R2?
Alternatively, move R1 and R2 to after the instrumentation amplifier. The values can then be reduced by a factor of 10 and a 1nF capacitor placed across R2, to provide current when the ADC's sample and hold circuit takes a measurement or if the reduction in bandwidth is unacceptable, add a unity gain buffer, between the potential divider and ADC.
Another solution is to drive the 10k to 20k load, with a constant voltage and measure the current.