Pre-interview anxiety

I'm currently a long-term substitute teacher in a kindergarten special ed classroom in Pennsylvania, but I applied to be the long-term teacher and I have an interview with the district the day after we come back from Thanksgiving break. I want this so bad because I love the kids and the work I'm doing, but I'm extremely anxious. I want to go back to school to get my master's in special education and getting this job would help me do that, but even though the special ed team has done a lot to catch me up to snuff I feel lacking and there's still some stuff that I don't know in terms of filling out the paperwork.

To top it off, they want me to do a five minute teaching demonstration and I don't even know what that would look like because while I know how to teach the material, I don't know to whom I'm supposed to be teaching the material. Am I supposed to do a real life demonstration with one of my kids? Am I supposed to pretend one of the panel members is one of my kids? I'm honestly freaking out and I'd really like some advice, or an idea of what to expect, or even encouragement. Please and thank you in advance.