Apart from abduction in a more widely thought of sense, one angle of inquiry could revolve around a child trafficking syndicate I suppose...
But even for that, who would think of going to a place like Kendall, for god's sake, to do that??!!
Unless someone had been in that precise spot before, you wouldn't even know it existed, let alone what it looked like up there. It's not at all a major thoroughfare, just a few houses, a couple of streets. That's it!
And, as a criminal, if you were concerned about being seen/chased, there's really no way out apart from the very same street you drove along to get to the vicinity of the house. I know the point about tracks in the bush has been raised but again, you'd have to be even more a local to know about those than you have to be, to know about Benaroon Drive!
The only other alternative, I reckon, if it were a non-local, is someone who has researched that particular spot and knew that it would be a place to pick William up from.
Just can't get my head around what a random person would be doing there.