While shop owners are devising promotions and sales to start Sunday shopping with a bang, shopping centre owners are planning activities to help draw customers and emphasise the family friendly aspect to the new trading regime.

Free shows, children's activities and competitions are planned.

"Sundays are all about relaxing with the family and having fun, so we're delighted to bring entertainment sensations Justice Crew, Ricki-Lee and more to Westfield Whitford City and Westfield Carousel to create a great day out for the young and young at heart," Malcolm Reed, Westfield's regional manager for WA, said.

Darin Maher, senior centre manager at AMP Capital, which owns three shopping centres in Perth, said: "We will be focusing on providing free family entertainment activities every Sunday during September and October."

Garden City Booragoon, Karrinyup and Ocean Keys in Clarkson will put on activities for the official start of Sunday trading on August 26.

Westfield shopping centres at Whitford City, Innaloo and Carousel will be open tomorrow, taking advantage of existing trading laws that allow a limited number of Sunday openings annually.