Back in 2015 he was spending a lot of time on the floor, building spaceships and star destroyers with his then five-year-old son, Aiden, and the pair ruminated over what Lego range they would invent.

When Aiden suggested a beach range with lifesavers and surf boats, Mr MacRae immediately recognised the potential of a quintessentially Australian set.

And then he saw that an even greater opportunity had presented itself.

Mr MacRae was recovering from treatment for stage four skin cancer. Here was a way to promote sun safe messages, with figurines that wore hats, long sleeves and – for the first time in Lego history – sunscreen.

"This is something that Australians can get behind," Mr MacRae said.

"It will at least normalise sunscreen among kids, when they see it on their heroes.

"We can still celebrate the beach. We can't be afraid of it. We just need to be smarter about when we go down there."

Lego has a website where it encourages its fans to submit ideas and vote on the best ones. Those that get 10,000 votes qualify for review, and if they pass the relevant tests they go into production.

Mr MacRae and Aiden sent their designs to a British company that manufactured the prototypes to be submitted to Lego, and they have a year to reach the vote threshold.

"It's been an exercise in promoting sun smart awareness campaign, but also encouraging Aidan to back his own ideas, to show him this is what you do with ideas.

"You put it out in the public and see if people like it."

The range includes a rockpool, life tower, lifeboat, jet ski, shark patrolling drone and quad bike, and each of the four lifeguards are named after celebrities that have experienced skin cancer: Hugh (Jackman), Nic (after Nicole Kidman), Keats (after Diane Keaton) and Bob (Marley).

There are also two surfers – Brick Fanning and Lai Beachley. All wear sunscreen.

The latest Cancer Council NSW sun protection survey showed a slight increase in the proportion of people who wore sunscreen since 2003, but a 5 per cent drop in the number of people wearing hats.

People were most likely to be burnt on the face, head, nose or ear.

The MacRaes' Lego campaign has drawn support from Cancer Council Australia and Melanoma Institute Australia.

The Crown Princess Mary Cancer Centre at Westmead Hospital, where he has been treated, is seeking support from its eponymous patron, whose Danish credentials might carry more weight at Lego headquarters in Denmark.

The construction of the range has started and faltered along the arc of Mr MacRae's health.

Aiden conceived the idea while Mr MacRae was recovering from treatment for a tumour on his lung, the second manifestation of a melanoma that had been removed from his earlobe a year earlier.

They launched the range in October last year. Then a month later Mr MacRae started suffering seizures and doctors discovered a large tumour on his brain and more in his lungs.

He spent the final months of 2016 undergoing radiotherapy and is now on a new drug therapy.

"It's kind of a last ditch resort at the moment," Mr MacRae said. "That's what they say, but I'm confident they'll sort it out with this drug."

After all, Aidan already has his heart set on a new Lego range – a jungle set – and Mr MacRae is pondering how it might be used to raise awareness about animal extinction.