Using a mouse breaks one of the CORE rules of the gameboy. There is no wiggle room here. If the mouse is that important to you, then this may not be the right jam for you I'm afraid.
I personally don't have any accessibility issues but I still think it's dumb to make the games harder to play for certain people for the sake of principle. Game jam constraints are meant to foster creativity, like the 4 colour rule, but this seems completely unnecessary. It is your jam though, so run it however you like.