Use the Windows drivers for your stick, which produces a serial COM port. You can then map that port to your VM, assuming the driver baud rate, etc. are configured correctly. I am using a Debian VM currently.
How would you go about mapping that port? The stick shows up in Device Manager as Ports (COM & LPT) > UZB (COM4). I don’t see anything in Hyper-V manager that lets me map a com port to a VM.
Everything I’ve googled on the subject is very discouraging, and implies it just can’t be done. If you and your son are doing it, I’d appreciate some more detail.