I have been where you are. First it is good to be a bit nervous, you are doing something that you haven't done before. I am a former music teacher with pre k-8 experience and I recently Subbed in high school, I was a bit nervous with this new age group. It keeps you on your toes. I am nervous every new school I go into, with their expectations and what the students will be like, etc. Then you get over it. If you don't, then there is a problem
Basically just address the problems you see. If you get to a point where you don't see any more problems, then it is time for them to move on. Your decision to lay everything out on the table will really help YOUR nervousness. I hope they appreciate you honesty. You'll find you know a lot more than you think you do.
Next, I'd get a flute book (I like Nancy Toff, The Flute Book) because you'll know most of what is in there, you'll learn new stuff, and you'll have a quick resource for trouble shooting. If you can't explain something or haven't experienced it, it would help to have a resource. It is good to have the answer sheet in front of you
And DON'T be afraid to say "I don't know, but I will have the answer for you next lesson."
Your job is to do the research and communicating the learning so they will benefit. Setting goals with the students is good too. Long and short term. Ask them where they thing they need to improve, and figure that into the goals. Having a basic plan will let things fall into place easier.
Lastly, you HAVE to start somewhere. I started when I was in 8 grade teaching a 7th grader who had just picked the instrument up. I think she played through college, and probably still now. I taught an adult when I was in 8th grade as well- it is hard to get over being someone's peer or inferior, and to feel comfortable in teaching shoes, it just takes time and experience.
From the band music teacher point of view, this mind you is a bit tongue and cheek- but the truth, but you only have to stay one page ahead of your student. I don't recommend it, but technically it works.
SO don't worry, be honest, be confident (you have your prior teaching experiences), get your resources in order and HAVE FUN!!!