I'm afriad that you can't get the multiple entry visa, you can only get the single entry tourist visa for you and your family, it is enough for your travel itineray within the mainland China. You two children also need apply for seperate Chinsese tourist visa, but the visa application form should be signed by you. The single entry visa fee is 30 Ringgits per person, you have to pay 120 Ringgits in total. it takes 4 working days.