Just using .accName gets the property fine, the reason the exception is being thrown is that it is of type "unknown".
After many varied attempts at making it work, I have come to the conclusion JScript sucks at this stuff
Strangely enough, if you run it when signed in, all the children have accName type as unknown except for the advertisement area which actually returns a string containing the url of the advertisement. Even though the proper accName of that child should just be "Advertisement", with the url actually being the accName of another child of the Advertisement child, which I don't understand at all.
The only property that seems accessible is accChildCount, all others return type "unknown". Pity because this seems quite fun to play around with if it worked