On career day, you are not just there to talk about how your spend your day. You are also there to inform the students about a potential career. If you enjoy being a project manager, you can explain to the students why your job is appealing. However, you can't "oversell" the job and make students who are ill-suited for management think they're destined to be project managers. The key is to "sell" the position for what it is. One option is to emphasize that it is less a job and more a consequence of moving up in an organization. Tell a story from your pre-management days to get this across. Another idea is to talk about the personality traits that make a good manager. Relate your own experiences to back up your observations.
Depending on how young the students are, they may not know exactly what a project manager is. You can use your presentation time to discuss the role of project managers in the community. Discuss the actual projects you have coordinated, and how these have been used. This will show the students how project management is relevant to their lives. Or talk about well-known institutions in the community where project managers are employed. Examples include engineering and construction jobs, market research projects and public works projects. You may generate more interest in the profession by mentioning these and other prominent examples.
If you are a project manager, you probably work with a team. Some project managers work more closely with their people than others, but almost all are responsible for a team's work. A presentation on how you and your team work together is a good idea for career day, because it gets to the heart of what a project manager does. You can, for example, focus on how you employ specific strategies to motivate your team. Or you can talk about the issues that can arise in managing teams of people, like office politics and conflict.
Bring samples of your team's completed project work if you manage projects that students might find interesting. For example, if you work as a game development project manager, bring in a game that your team made, load it up on the computer, and demonstrate it. You don't need to work in the games industry to build your presentation around an interactive demonstration of what you do as a manager, however. If you work in any manufacturing industry, for example, you can bring some of your goods into class, and explain how your management skills make it so that these goods are produced on schedule.