Hi, the temperature will be abour 8~16C at that time. You can bring long-sleeved shirts and sweater, plus one coat in case cold at night.
There are many attractions worth your visiting in Shanghai, such as Yuyuan Garden, The Bund, Jade Buddha Temple, Oriental Pearl TV Tower, Zhujiajiao, Qibao Ancient Town, etc.
You can buy some local products, such as Gu Embroidery and Chinese silk.
As to eating, you should not miss Houyin Fish, Canned Anchovy and other local specialties like Pudong Chicken, Shanghai Juicy Peach.
You can buy Jade sculpture, wood sculpture or stone sculpture as souvenirs.
For a better travel routs, you may refer to these well-arranged Shanghai Tours(https://www.travelchinaguide.com/package/shanghai.htm). Wish you a good time in Shanghai.