Lecture organizer seeks event planning software

We organize adventure and travel lectures and are looking for software that supports us in event planning (event management, multimedia show organization).

We have the following requirements for the software:

• Task planning
• Renting halls
• Organizing advertising partners
• Inviting guest speakers
• Managing our own speakers
• Coordinating helpers
• Scheduling and data exchange
• Juggling appointments so that there are no overlaps
• Shared calendar that runs stably on Mac and Windows
• --> IMPORTANT: at least a six-month view in the calendar
• Shared access to data from three locations
• Marking options with different colors would be good
• Windows and Mac compatible

Three to four software workstations are planned.