The haze tends to cause sore throat and congestion so I'd say keeping your children as hydrated as possible will help alleviate any signs of dryness or even stave off the abovementioned symptoms.
If the child is old enough, masks can come in handy to keep the haze from annoying the child too much. If you're using the air conditioner, make sure the filter is as clean as possible because it will defeat the purpose of staying indoors if both "air qualities" are just polluted.