You can do whatever you want, but the spirit of the jam is to make things in the style of the limitations of the original Game Boy. Two things worth noting:
It's a game jam, so it's a great place to try learning something new (for you, it might be how to do controller-navigated menus)
Nobody is forcing you to stick within the rules. If you do have mouse controls, you'd likely just be sacrificing potential scores in the "Gameboy Soul" category.
The jam page does say to use the same control scheme, and mice weren't too common with the original hardware. I doubt many people would mind, but it may count against you. If you're really, really stuck and don't have time to learn, you could forgo having options and just display a "Press start to play" titlescreen so the player just has to press one button to get into the game.
