Visa Application for accompanied children for holiday in China

My children will follow us to China for holiday in December. All of us are holding Malaysian passport and Singapore PR. We would like to apply L visa personally. Do my children need to come in person when submitting the application at Singapore CVAC? Can one member family submit on behalf of the family? For children, are their passports as proof identity sufficient? Do we need to bring their birth certificate? They are born in Singapore. Thank you.