Your conscience is your own to deal with, I agree with others here that it is unethical to lie about something like volunteer experiences on an application but I personally don't feel it is "immoral" (I would reserve that classification for activities that cause harm to others, which I don't think this really would). While it is true that it doesn't exactly indicate a strong value system such as one would hope to find in a would-be physician, it's not unlike the routine resume padding and embellishments that go on every day in the corporate world.
That said, assuming you don't have any huge moral qualms about doing such a thing, you have to ask yourself if the payoff is worth the risk. It's highly unlikely that anyone would ever check up on something like that, but if you do get found out somehow--and you never know who knows who, or who's going to say what in a letter, and I speak from experience as someone who has been surprised more than once at the weird and seemingly random connections life can make between apparently unrelated people and events--you're pretty much ruined, as lying on an application, even a relatively small lie, will essentially gaurantee you a rejection and possibly blacklist your name at other schools as well. If you got caught after acceptance, it would likely be grounds for the revoking of said acceptance or expulsion from med school, if it were found that you blatantly lied. And for what? A very slightly more impressive EC? It just doesn't hold up to a cost/benefit analysis--the risk of getting caught is very small, but the price if you are found out is potentially huge, and way out of proportion to any small benefit it would have for your application.
