The main showpiece of the day's horse racing card is the $540,000 New Zealand Trotting Cup which is expected to start at 5.34pm.
At 1.02pm, the cup is due to arrive by helicopter, piloted by Rugby World Cup winning captain McCaw, with two special guests on board.
One of New Zealand's oldest war veterans, 103-year-old Neil Harton will experience his first-ever helicopter ride.
Harton, who spent five years in the Navy and recently returned to the 70th Anniversary of the D-Day Landings in Normandy where he served in 1944, will also be joined by fellow centurion Jack Marshall.
Christchurch's Marshall, an RNZAF air gunner, was involved in many acts of bravery and was awarded the Distinguished Flying Cross (DFC). On his first tour, he survived a ditching in the North Sea for 16 hours due to the loss of port engine from enemy fire and on his second tour survived two airfield crashes due to pilot error.
It's expected they will get a hero's welcome when they touch down in front of the large crowd.
The ever popular Best Dressed Lady and Best Dressed Man competitions are going ahead today.
Dance duo Sweet Mix Kids will play on various stages throughout the day while singer Hayley Westenra will perform the national anthem before the big race.
Gates open at 11am and the first race is at 11.55am.
Addington Raceway chief executive Brian Thompson says despite a cloudy forecast, no rain and minimal wind should make for a great day out.
Police are asking people to look out for each other throughout the day.
Senior Sergeant Phil Newton said there will be experienced staff at the gates to ensure no one enters the event intoxicated.
He said those consuming alcohol should have plenty of food and water - that way they can last the distance - just like the horses.
The event will also give a much-needed boost for the city's hospitality sector.
Director of the Pedal Pusher Bar in Addington, Prateek Rana says the day should bring plenty of patrons after a challenging year with Covid-19.
Rana says the pandemic has dampened business in 2020 with a tonne of cancellations at both Horncastle Arena and the rugby stadium.
Addington's Miller Bar is even expecting a few regular out of town visitors - patrons manager Michelle Cattell calls the "yearly locals".
