Yeah. The motors aren't usually moving incredibly fast so this would probably sort of work unless, of course, in the unlikely event that both readings have interference.
I would really quite like to try some of the hardware filters that I have seen mentioned elsewhere on this forum. Do you have any idea how to implement them? This will allow me to keep my tested code the same, keep the fast response to the switch closing and reduce the chance of getting two bad readings.
I am also wondering if I could increase the resistance of the pull down resistor to deliberately make things unstable, check that the hardware filter works correctly then reduce the resistance back to 1k. Does that sound like a sensible way of solving (and knowing I've solved) this rare intermittent fault?