Why do they need integer operations? Students can see that the distance between $(-1,3)$ and $(2,3)$ is 3 without knowing how to subtract $-1$ from $2$. For example, they could plot the points on the plane and count the units to get the distance. This is in fact good preparation for integer subtraction. I think maybe you are thinking about the formula for distance, which would indeed require integer subtraction. But you don’t need to use the formula.