The Everything Aussie Festival in beachside Lang Park is being held as part of the Catholic Church's Days in the Diocese celebrations.

A spectacular highlight of the week-long calendar of events will follow tomorrow night when 5500 residents and pilgrims attend a Mass celebrated by Bishop Peter Ingham and 80 international bishops and priests at WIN Entertainment Centre.

World Youth Day spokeswoman Kylie-Ann Haynes said the Everything Aussie Festival, which starts at 12.30pm, would feature a full program of family activities including amusement rides, sideshow alley, international and Australian food and live entertainment.

Sporting clinics will be held by St George Illawarra Dragons and Cricket NSW.

A koala and kangaroos will be available for pats, while there will also be sheep shearing shows.

Performances and entertainment will be provided by The Little Ngargens Aboriginal dance group, Tongan Youth Dancers, Bowral's Innocent Witness, MKUD Makedonija Wollongong Dancers, former Australian Idol contestant Joseph Gatehau, Nigerian pilgrims, Noelle from the United States, Louise Robards and Mark Raue and Kiama's Dogmatics.

The "Wollongong Olympics" will begin at 3.30pm and will feature 11 international youth teams pitted against an Australian side in such events as volleyball and relay races.

"The day is all about celebrating and seeing how our Aussies party and have fun," Mrs Haynes said.

Attention then moves to WIN Entertainment Centre for a WYD Commissioning Vigil Mass that begins at 5.15pm with entertainment by the 30-piece WYD Band and Choir, followed by the Mass from 6pm. The Mass is expected to take about two hours.

On Sunday, 500 pilgrims and their hosts are expected to attend an NRL game between St George Illawarra Dragons and the Canberra Raiders at WIN Stadium.