Going Home 24 Hours Visa?

Hello,

I am Canadian and I will be visiting New Zealand and Australia this December (2018). On the way home I will be flying from Sydney ---> Kunming (layover 3hours 30 minutes)----> Nanjing (layover 1hour 40 minutes)----> Vancouver. Will the 24 hour direct transit work for my Nephew and I or do we need to apply for a visa because we are stopping in two Chinese cities?

Thanks for any answers you can give