Appointment/Calender/Invite System

I am looking to be able to send diary invites/outlook appoinpointments to lists of email addresses and possibly mobile/cell phones AND then be able to change them if need be. Eg I send an appointment/invitation to 3000 email adresses for Jan 5th. Then if date changes to the Jan 7th,? be able to send them an update, changing it to that date or cancel old appointment and send new.