Considering that I used to be extremely quiet and kinda shy too, I'll see if I can offer you a few tips that my college speech professor gave me. (Obviously, I doubt you'll be able to take a semester of speech before you do this, but I still might be able to full a few magic bunnies out of the hat for you).
First, pray (more). Second, breathe (deeply).
Or you could do that in reverse. You might not be able to pray if you're not breathing...
After you've sought the Lord's will,
keep seeking while you continue to prepare yourself
(Skip through this list if you want ideas about the speech itself, not the structure...)
With those building blocks in place, you can continue on to build the wall. Which means you might like to find your comfortable way of speaking. It's a class of 8th-graders, so the best kind would probably be an extemp speech, but you might find it more comfortable to do something else. Here are the pros and cons of each method:
1) Written/outline/manuscript speech--where you can take a manuscript of however papers you want with you and read your speech from the text:
PROS--well most people are most comfortable with this one. It's easy to write out, easy to read from, and easy to estimate how long it will take you (with a font of 14pt, it takes roughly a minute per page).
CONS--it's hard to connect with the audience, since you'll be reading from the MSS instead of looking at them the whole time, so eye contact is a biggie. Also, if you think of something you want to say during the speech, you most likely won't be able to include it unless you find a good gap, but then that might interrupt the flow of your speech. This is also not generally a good idea for small audiences, since it's a bit too formal-ish.
2) Extemporaneous speech--where you can either use note cards, an outline, or visual objects to remind you of the main points you want to make in your speech:
PROS--since this one has your main ideas set in stone, it's a concrete way of speaking without the awkwardness of the MSS speech. For this one, you can use note cards to help you with particularly powerful lines you want to include as well as the main ideas of your speech (and things like quotes, statistics, names of books, etc.) without restricting you to a step-by-step procedure that might sound robotic. It's also a good way to keep eye contact with the audience and to be actively engaged with answering Q's and the like.
CONS--it's not the best of any of the types of speeches. If you want flow, the MSS speech is best. If you want connection, the Improv speech is best. If you want eye contact, the memorized speech is best. This is, however, the most rounded speech of the four, so it's usually the most suggested one.
3) Memorized speech--this is one I don't recommend, but it's essentially the same as the MSS speech except you memorize your whole speech:
PROS--good for long meetings where you need to maintain contact with the audience.
CONS--takes a lot of practice and time. Also, if you lose your place, it's hard to pick up your speech; and if they have questions, you need to put them at the end of your speech.
4) Improv speech--I'm not going to explain this one because it's basically not preparing as much and just "going on the fly" on the day of. You'd be better off doing the Extemp speech.
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No matter what kind of speech you do, however, remember to practice as much as you can. Do it front of your family if you're comfortable with it and get feedback. OR you can do it in front of yourself with a mirror and a tape recorder. This is just to get more comfortable with your speech--to solidify it in your brain and get a grasp of how long it'll take you.
Once you know what type of speech you want to do, you can start coming up with ideas. Actually, first you should decide on a thesis (even if it's not final, just so you have a main idea in place) and then you can come up with ideas. Personally, I suggest using the basic three-point extemp model so you can bring 10 or less note cards with you main points and "supports" (or whatever you want to include) written in them =)
As for what you can talk about, I might suggest doing just a quick half-minute to full minute introduction on why we write (just like writing a hook to your story--"why should I read?") and then give them another half-minute or so of a little "backstory" on who you are so that they're not zoning out for the rest of the speech. Then you can build your points.
For what you want to say, I'm going to ask you questions about writing if you don't mind
Q's: At what level of writing did you start? How did you start writing? Have you always liked writing? Is writing a gift, lots of hard work, both? Why do YOU write? What is your purpose in writing? Why should we care? What's in the power of words?
As for keeping it interactive, a visual of any kind would work, even the audience
If you want to do something fun, maybe you could have each of them pull out a piece of paper and pencil and write something for you, and you would write something for them. OR ask a couple kids for a quick introduction about themselves (favorite color, age, etc.) and then relay it back to them in "story" form, to show them that everything we do and say is really the makings of a story.
Or, you could bring your own visual (a simple pen, piece of paper... or something "ugly to look at" like your original rough draft--the one covered with highlights and etc.--to show them everyone starts somewhere. You could even bring a one page story filled with doodles that you wrote while you were younger or something).
Anyway, those are my suggestions
If you want anymore ideas, I can pool a few quotes I used from a speech I did on writing. Otherwise, I'll spare you from reading anymore of my wordy monologue <_<
God bless
I hope this was more helpful than annoying...
