Usually, Hong Kong and Macau will be in hot summer in the middle April. Shanghai will have plenty of sunshine but comfortable for traveling outside. You may need a thin jacket in early morning. Beijing should be in the early spring, so a windproof jacket and long-sleeved shirt should be prepared. As for children, please take warm jackets for thme.

Sweater in Beijing and T-shirt in Shanghai and Hongkong.

do i need wear down if i stay Beijing in April 1 to April 6

For me, jeans and shirt is fine. But just in case, take a warm clothes with you - the weather is not that stable recently, bot not cold any more..