WeChat requires iOS 9 (minimum) so your iOS 10 is compatible. However, there may be a hardware requirement that your iPad does not meet.
(iPad) Compatibility
https://itunes.apple.com/us/app/wechat/id414478124#?platform=ipad
Requires iOS 9.0 or later. Compatible with
iPad Air, iPad Air Wi-Fi + Cellular
iPad mini 2, iPad mini 2 Wi-Fi + Cellular
iPad Air 2, iPad Air 2 Wi-Fi + Cellular
iPad mini 3, iPad mini 3 Wi-Fi + Cellular
iPad mini 4, iPad mini 4 Wi-Fi + Cellular
12.9-inch iPad Pro, 12.9-inch iPad Pro Wi-Fi + Cellular
9.7-inch iPad Pro, 9.7-inch iPad Pro Wi-Fi + Cellular
iPad (5th generation), iPad Wi-Fi + Cellular (5th generation)
12.9-inch iPad Pro (2nd generation), 12.9-inch iPad Pro Wi‑Fi + Cellular (2nd generation)
10.5-inch iPad Pro, 10.5-inch iPad Pro Wi‑Fi + Cellular
iPad (6th generation), iPad Wi-Fi + Cellular (6th generation)
iPad Pro (11-inch), iPad Pro (11-inch)
iPad Pro (12.9-inch) (3rd generation), iPad Pro (12.9-inch) (3rd generation)
and iPod touch (6th generation)