Feature phone data plans are $15/month and are completely optional- that includes QWERTY phones like the Pantech Matrix. Those might work for you, momof3. The keyboard makes it much easier to enter calendar events and etc.
While the BlackBerry is a special case in terms of working best only when there's a data plan attached, you might try another dealer who won't pressure you into a data plan for a Windows Mobile phone like the BlackJack II, Epix and Pantech Matrix Pro (comes out next week). Generally AT&T corporate stores are less pushy than those dealers not owned by AT&T. If your son already has AT&T service and a SIM card, the other option is to not get the phone through AT&T at all, but rather pick up a used phone and simply insert his SIM into it (thus no plan change required).