Your credit card will be pre-authorized just like when you book a hotel room to reserve your tour or shuttle booking. Bookings may be cancelled up to 7 days prior to no problem.

Cancellations 5 days prior will incur a 50% charge and if you cancel 3 days (72 hours) or less prior to you will be charged 100% of the tour or shuttle cost.

I know stuff happens so an equivalent Gift certificate or other may be offered depending on the circumstances should you need to cancel some or all.