Tipping on private tour?

[DISNEYFAN3260]

Thanks to some great info and recommendations on the boards, we booked a private tour on St. Maarten with Bernard's tours during our August trip. We will be a party of 10, adults and teens, and we hope to stick to more historical/cultural sites and spend less time on the beach so this seemed the way to go. I've never done a private booking before. Would anyone mind telling me if I should plan on tipping 20 percent range for the driver (assuming a good experience), or is there a different standard in a situation like that? I need to plan ahead now to save for cash needs during the trip. I'd appreciate knowing what others have done. Thanks for any help!

 

[DISNEY FANTASY]

10% is fine. They will be very pleased with that. No need for 20% that's a Disney thing.