
Ah, yes you’re right — half dollars. Either way, though, 31 U.S.C. §5112 isn’t a constitutional limitation from which even the remotest derivation would be illegal. An authorizing act of Congress could supersede §5112 and allow the minting of coins bearing the likeness of anyone living or dead, as it did in 1926 before §5112. You claimed, though, that they’ve “never put a living president on any coin ever,” which makes it seem like this is some sort of watershed unprecedented moment. It is not.
Also keep in mind that the commemorative half features Washington’s face overlapping Coolidge’s and the reverse features the Liberty Bell, which is clearly symbolic of the nation’s freedom (reverse) and progress from founding to the (then) present by showing the first president to the most recent at the time. The symbolism is vastly different than putting one person on each side of the coin. Your point was also that there is precedent, which is both out of context and currently unauthorized