I wonder if any of their 'shared' options might work for you? Have you looked into this yet?
Any basic flip phone could suffice, although I'll be honest. Texting much on those phones (even some of the feature phones) can be a chore after you've been using iMessage on an iOS device.
Going on the web site and configuring a phone as a new user should tell you if it requires a data plan.
My iPhone 4 looks to be having some issues and may not be around for much longer. In the last year I got an iPad Mini, w-fi enabled and with the optional data plan with AT&T that I can turn on and off.
I am thinking of replacing my iPhone with a simple cell phone I would use for calls and texting and simply add the iPad mini to my plan with AT&T so it's always "on".
Crazy idea or not?
Does anyone have a suggestion on a basic cell phone for calls and texts (preferably no data plan or minimal so I don't get charged monthly for both devices by AT&T).