Helmet arguments are easy, if people are being honest, and can be resolved by answering one simple question: Would you let your kids ride their bikes without one?
As to the OP, seriously, consider what it takes to complete your ride, and plan accordingly.
For me, that includes comfort gear (i.e., bibs, jersey, socks, clipless pedals, etc.), safety gear (helmets, gloves, hydration/nutrition), and "what-if" gear (Road ID, driver's license, phone, tube/patch kit, pump, tools, cash, etc.).