Ah, this is posted in the wrong game jam (Last years').

Any way, attending is mandatory. At least the first day for theme reveal, registration (Which I assume you already did), and team formation, and last day for game submission and demoing/presentations.

Whatever goes in the middle depends on your team. However, I highly encourage you being there for the experience, having someone to help in case you have any problems (Like, coding or project wise), networking and interacting.