I think your height will be the biggest issue with a DR650. DRZ may be a bit better, but it isn't very good above 60. Many tall riders complain about the DR650 - not so much seat height as seat to peg length. At 6'6", there's only so much you can do.
The three of you on the same bike would probably be ideal, but it might not be feasible. I think the XRL may be the ticket for you guys and the DR for her.
Dare I say it as I am a HUGE DR fan, but a KLR may be the better choice for bigger riders. An older F650 would probably fit into your price range as well.