You’ve given so much thought to how your field study is going to happen, and your students are going to want to know what is up too. Prepare them in all the ways above. On the large scale, when is the field trip happening within the semester? Some students may need to coordinate its timing with other aspects of their lives. On the smaller scale, when in the day is the field trip leaving and getting back? And by what travel modes? Each of us have rhythms and schedules of our lives that may need to be thoughtfully coordinated with the field trip (e.g. medications, dietary, etc). This kind of active guidance ensures that students get the most out of the learning experience while providing support for students who have not gone outside of the classroom before.
Murphy’s Law… Things happen… It is good to think through what the uncertainties are for your upcoming field study as part of the planning process and as an exercise that prepares you to adapt if the need should arise. What are you going to do if it rains the day of your field trip? What happens if a student misses the field excursion for an unexcused or an excused reason? What are other foreseeable disturbances to your grand plan? Who are you relying on for logistics, and might they flake? Are there Plan B’s you can make now? For some of these, you might research the relevant College policies pre-decide what your adaptation would be. For others, perhaps there is educational value in the uncertain nature of what you’ll find in the field.