Do I need a reservation for the Cross Island Ferry, the North Ferry and the South Ferry? What are the fees for a car with 2 passengers?

Around 70$ for vehicle and around 15$ or additional passengers. You do not need a reservation. But it would be recommended. Also if you ever go as a walk on without a vehicle its easy to do without a reservation.

Ferries do sell out so a reservation is best. Fees vary so check the website.