Recognize and respect they will have a considerable amount of autonomy on campus and while this may be what they've dreamed of it will probably provoke some anxiety and confusion.
Your role is shifting to more of a coach or advisor; you have every right and responsibility to share your opinion and advice. Any attempts to "make them" adhere to your rules will probably fail. Stay connected and negotiate.
Shift responsibility in their direction where possible, encourage them to solve their own problems and reach out to resources on campus for help (RA, academic advisor, faculty, health services, counselors)
Have a discussion about your and their concerns or expectations about alcohol use, time management, budgeting, and academic outcomes.
Place more focus on discussion about the content of their courses and not so much on their grades. The first few terms can be a major adjustment and they may not be able to get the grades they were accustomed to in high school.