Ah, finally- proof that mechanical keys and electronic fobs are completely equal! Except, of course, for the fact that fobs are so much better.
I would agree with you on the alcohol but note that I recommended 91% rather than 70% for exactly the reason you mention. 99% would be even better but 91% is the purest readily available in local stores. 99% is an industrial mix and much harder to find and purchase in small quantities.
I also specifically recommenced rubbing alcohol (isopropyl alcohol is called rubbing alcohol in the US) because it will not attack anything inside the fob, the electronics, the plastic or the rubber. Using something like denatured alcohol is risky because it is usually denatured with a fair dose (technical term) of acetone which attacks many kinds of plastics and is hard on some electrical components (anything coated, varnished, the silkscreen on the board itself, etc.) I have found that the 9% water in 91% alcohol will evaporate pretty fast and does not leave any water behind.
But by all means, if 99% isopropyl alcohol is available, it would be better than 91% for cleaning anything electronic for exactly the reason you mentioned; less water is always better around anything electronic.
Brian
I washed the key for my old bike once and... nothing happened.
In fairness, I have also washed my FOB and... nothing happened.
I didn't do anything with the fob when I washed mine since it worked and the FOB has some weather sealing. Brian's suggestion of cleaning it with rubbing alcohol is good advice with the exception that rubbing alcohol is usually 70 percent isopropyl alcohol, what you want it a 99 percent isopropyl alcohol. Rubbing alcohol has too much water content for use in electronics.