If you want to expand it eventually, start with imagining the trailer. Write a script that has all the elements of a solid trailer in it (this is a lesson I keep having to learn). Read the parts of the script for the trailer out loud to your kids. Can they see it? Does it grab them? Have a group of community theater people or even a dinner party of your friends read your complete script out loud to a small audience. Does it work?Do they laugh at the funny parts? Record the reading. Listen to it many times. Does the dialog excite you enough to give up countless hours in the sunshine to bring this to life?

If so, do some character sketches. Refine the differences between the characters. Is the piece action driven? Is it dialog driven? If action, you probably want to do it in CG and in 3D (seems to be the rage now). If dialog/story driven, you can do it in any animation genre.

Once you choose a style and form, begin storyboarding. Later you will turn the storyboard into a slide show with the dialog recording you did.

The more time you spend on these pre-production elements, the better the final project. We spent 6 years in pre-production on our film. By the time you are at this point, the hardware / software options might be radically different. Let me know how it goes!!!!

Sounds good.

Depends on how much you want to spend, but really at the beginning pen and paper is enough...maybe Screenwriter Pro.