"Caleb hardly slept a wink last night because he was so excited about meeting the players," Mr O'Brien said. "It is outstanding that I can bring my kid along to say hello to the likes of Shaun Johnson.
"We will be here for the entire tournament and this is a great way to start the trip."
Duco Events chief executive Martin Snedden believed part of the ongoing success of the NRL Auckland Nines is the excitement in the lead -up to the tournament.
"Auckland really turns it on for the Auckland Nines," Mr Snedden said. "Events like the Fan Day create a buzz in the city, and New Zealand and overseas fans get to meet their rugby league heroes."
Warriors star Tuivasa-Sheck said it was a "buzz" to meet so many supporters face-to-face.
"I've been signing things for people from all over the world and this is perfect for setting the scene for the tournament for the players as well as the fans," he said. "We are very excited about the tournament and the prospect of the Warriors playing together again as a team."