It's been a while since I've set a multi AE network up but I believe when you use the extend option the AEs will try to connect wirelessly together, not what you want.

As someone already said, put the TW in bridge if possible or swap it for a regular DSL modem. If it can't be swapped due to on-board telephony or STBs, keep the wifi off and use the DMZ mode to share the public IP with one of the AEs. This will give you an all Apple network with one AE as the router and the others in bridge mode. I've done it out here with ATT Uverse where we have to use the ATT gateways.