It sounds from the other post that this is a fairly short trip?
In that case, I would suggest that you save the trip to mainland China for another time when you have the time to visit some other places in the area. Like you said, visas are an expensive hassle, and it would really be a shame to be in that area and not visit some of the amazing scenery like Yangshuo.
Could you plan to meet up for dinner at a (kid-/foreigner-friendly) restaurant? You'll need to eat anyway, and you can always use the kids as an excuse to cut things short. Just point out when you're making the plans that the kids need to be in bed by a certain time.
Is your H's family from someplace small? If so, it might be good to have a local contact if you ever do visit.