Carrying on from Magsi's decription:
CP is such a vague term as it can mean it affects only one limb in a minor way such as being a bit stiff, a slight limp etc, to being totally incapable of movement including poor head control. And it can impair vision, there can be poor speech or no speech, there can be mild or severe learning difficulties, epilepsy can be more prevalent with CP. A long list!
So really each person with CP is very different.
I can't really think of a way to be prepared for your new job, I personally think the best thing is to meet the children first, then once you know what kind of problems they have, you can delve into a website which can give you an insight into their exact problems.
One thing I have learned about CP: my ds has many friends in school with CP, and they are all lovely, charming, (mostly) happy and easy to get along with. Hope this helps a bit.
BTW, Hi Magsi, hope the summer hols were ok, good luck for school for your ds, I'm sure once he settles in, he will enjoy school...it will be Christmas before you know it!!! (Read your other thread, am I the only one looking forward to School?!)