I use Ctrip for domestic China travel, and so far I have not had problems with them. My trips on CA have always been credited with UA within 1 or 2 days after travel, so I wouldn't worry about UA not crediting miles for UA tickets bought on Ctrip.

I suggest that you read the fare rules carefully. Since it's PVG-SFO-PVG, the rules are likely to be more flexible than SFO-PVG-SFO that most of us are familiar with.