I am making a reservation for March 8th. How far in advance if I cannot keep the reservation do I have to cancel without my card being charged?

At least 24 hours prior.

You must cancel 24 hours before your reservation.

For a definite booking i recommend 60 days if possible but you must cancel 24 hours before your reservation. If you can't get to it in time you'll be charged a ten dollar no show fee you must call up Disney or contact a cast member if it's due to disneys faults . I recommend the Minnie van service to make sure you get there in time .