Travelling w/ preschooler to visit relatives in Mainland

My wife would like to surprise her dad by treating him to a trip to see his relatives in mainland China, and she’d like to take our four year old daughter along to show her off to the extended family. They live in Fujian province, at least a half a day’s drive inland from Xiamen.

I can’t help but feel a bit nervous at the prospect. Have any of you travelled with a young kid off the beaten path on the other side of the Strait?

We visited Xian when our youngest was six and our kids did fine except for a mild case of diarrhea (probably due to poor food hygience).They have since visited other cities like Shanghai, Beijing, Suzhou, Nanjing; no real problem there.
It’s best to visit either in Spring or Autumn as weather could be quite extreme in the other seasons.We always had to visit in Summer though, due to school terms. Kids could get cranky in the severe hot weather, and dehydration is one thing to avoid.