We will be on Bonaire the last two weeks of Nov. Is it necessary to reserve a vehicle before we get there? Is it easy to rent a vehicle sporadically? I KNOW we will not need one all 14 days. I wouldn't rent more than 2 or 3 times.

We also plan to visit Curacao for a day or two. Will tickets be available a day ahead of time or should we make reservations now?

Suggest you make an initial reservation for a car and it will establish you with a rental company and then you can block out your days one on island. There are number of choices for reservations to Curacao but sometimes flights are sold out so you need to be flexible.