Others may conflict with established schedules. Still others may not elicit sufficient student or faculty support. In these cases, it's better to put things on hold, or to go back and re-design things. If you do not do this at an early stage, you will have problems later on. Make sure that each individual understands what you expect them to do, and when.
Someone needs to plan and monitor the academic component of the program.
Someone needs to plan and finalize all the arrangements for the trip itself, including airfares, hotels, ground transportation, meals, guides, etc. Neglecting this aspect of planning can lead to problems later on. If your program is open to outsiders, then you need to do marketing to ensure that you have enough participants. This means preparing information and arranging for publicity. Someone needs to be in charge of this.