Yes, you can bring along you children to the canton fair. How many days for you to make this whole route. That is different way of visiting on Macau and Zhuhai according to your time. It also depends on what are you going to see. At least one day on each place, Macau and Zhuhai. If you want to go to Guangzhou from Zhuhai before dark, the last bus leaves from Gongbei Bus station at 19:00. So, you should get there before that time.