Grant Funding, Spare Parts



I am the tech at Holualoa Elementary School in Kona, Hawaii. We intend to include 2 FarmBot Genisis 1.4 units in our application for grant monies. We would like to include costs for parts that may or are known to fail so that we will be able to keep the bots functional beyond the initial purchase with grant monies.
So my question is what parts are known or may fail and how many spares should one get?