As to the constitutionality of Trumps order, it certainly isn't as definitively unconstitutional as you seem to think it is.
https://www.theglobaltreasurer.com/2025/02/10/trump-orders-t...
Robert K. Triest, an economics professor at Northeastern University, noted that while a full discontinuation would require legislative approval, the Treasury Secretary might have some discretion to halt production.
“The process of discontinuing the penny in the U.S. is a little unclear. It would likely require an act of Congress, but the Secretary of the Treasury might be able to simply stop the minting of new pennies,” Triest explained.
That seems to be due to you miss remembering the particulars of the issue.
https://www.washingtonpost.com/politics/harriet-tubman-20-bi...
"The Treasury Department announced in 2016 that Tubman would replace Jackson"
So in one instance, we have cancelling of minting new pennies, ototh we have the changing of a picture.
I do think there might be viable authority to cancel the minting of the penny in the same way that there might have been viable authority for Biden to mint a coin and cancel debt. Seems to be similar rules at play there.
The secretary decides the amount necessary is 0.