The 1st generation Surface Pro uses 3rd generation i5 technology, whereas the 2nd generation Surface Pro uses the 4th generation i5 technology. This equates to slightly increased CPU performance, overall, a significantly improved GPU, and most of all, vastly improved battery life. In addition, I believe that the Pro 2 has some other small differences, such as increased resolution capability, afforded by the updated GPU. I could be incorrect in that assertion, however. There is the additional position on the kick-stand, as well, but if you are giving it to a seven-year-old, I would recommend a protective case, anyway.
Finally, if the seller listed the item deceptively or incorrectly, you have recourse to decline the purchase. Feel free to reply, or private message if you have any further questions regarding that issue.