A few questions first:
Are these workshops for the day of kickoff?
Who will be attending (students from your team, or students from other teams also)?
What are your goals for these workshops?
I think that you should answer these questions as a team before you begin to plan these workshops.
But anyway, here are some various ideas:
- Start with a team meeting (or just a new-kid meeting) to explain what FIRST is, how it works, and what its goals are, this way the kids know, overall, what they are trying to accomplish
- Demonstrate how to use some machines (Separate into several small groups for different tools and machines)
- Have a brainstorming session with different groups of kids (so you can get completely different and unique ideas)
- Explain what each sub-team does during the season
I hope this helps a little!