Are there other phones similar to this smaller size that I can use on AT&T that have wifi without having to trigger a data plan?
AT&T detect your phone and add data plan automatically. Recently I had big fight with their customer care. They refused to remove $20 data plan because now it is their policy if you use smartphone then you have to buy their monthly plan.
I would suggest go for MVNO like ptel or straight talk with these phones. You will save lot of money in long run