Never organised a school author visit before?
No idea how to start?
How do you get in touch with an author?
How much will it cost?
What do writers eat?
Here's a link to a downloadable PDF from the Society of Authors with loads of advice on organising Author Visits.
A Guide For
And here's more good advice from ContactAnAuthor -- a site run by authors, for authors.
You will also be able to, well, contact authors through this site.