How safe is ios password-protection?

Hi,

Forgive this post but there are quite a few questions in it.

I have an iPhone and iPad and used Pages on all devices synced to iCloud.

I have started writing a novel and am about to go on holiday where I'll hoping to be doing some writing by the pool.

I just wondered, how safe is the password-protection? Specifically, what I mean is, let's say my iPad is stolen but is password-protected, how easy is it to mount the device and copy all the files from it—including my manuscript?

I am being overly cautious here because:

a) I'm guessing your average thief in the country I am going to wouldn't have a clue how to do anything that technical

b) My novel is not worth stealing

However, I am interested either way.

If for whatever reason my phone or iPad was stolen, would changing my iCloud password do the trick to protect my documents?

Finally, if someone does steal an iPad or iPhone can they just plug it into iTunes and start from scratch? And how useful is the Find my iPhone service?

Many thanks.