If you simply connect both PlayBooks to your computer with usb connectors, your computer should assign drives to them ie: Z and Y.
Then you can drag & drop (or copy) files between them. It would be faster than a wifi connection.
It works well for me. Haven't tried wifi yet.
I see bluetooth connection is also available between PlayBooks. Haven't tried that yet either.
For wifi, Try accessing each Playbook thru Network access directly. Not thru Explorer.
That should show the files.