It's hard to give really helpful advice without knowing the students' need for English. Are they there to learn? Do they just want to chat? Has HR sent them as part of a company-wide program?
Additionally, how long is the class?
Take a look at my website for materials if you're stuck, as everything is geared towards adult learners.
English Lesson Plans | Heads Up English | ESL Lessons
You can use a lot of the speaking/listening materials to focus skills, such as skimming and scanning, summarization, presentation, debate, and so on. I've worked with a lot of adult students in the past, and even very high level individuals can learn to give better presentations, support opinions, etc.
Good luck, and let us know how it goes.