And with so many decades of camping experience behind them, they have seen virtually every campground faux pas you could imagine.
Asked to name absolutely the worst quality you could get in a campground neighbour, they say the answer is easy: noise.
Early in the morning or late at night, the last thing you want, they say, is a noisy neighbour in the tent or caravan next door.
And if you think the noisiest campsites are those filled with teenagers and booze-stacked chilly bins, you might be wrong.
At Mangawhai, middle-aged campers and toddlers have the finger pointed at them.
"I can remember one year there was a family behind us with a toddler," Liz says. "They came and played ball with the kid at 5.30am right outside our caravan."
Fergus Brown, chief executive of Holiday Parks Accommodation NZ, says it's sometimes the older campers who celebrate things such as New Year well into the night. "The young ones party hard but then about 1am they'll go to bed. The older ones have more staying power."
Liz Smith recalls being a culprit. One year a game of charades, complete with a friend miming being unconscious on the sand, had them shrieking with laughter.
They were so loud that the campground operators came around to warn them to shut up.
• Brown says: You can opt for a campground that groups visitors by age so young partygoers will be in one part of the park and families in another.
One thing that sets campgrounds apart from virtually any other environment is how close you are to your neighbours.
With sites just a couple of strides wide, campers are often sleeping almost within reach of each other with just thin pieces of canvas separating them. Privacy is an illusion.
In a caravan a couple of rows back from the Smiths, Rachel Liggett is camping with her husband and kids as well as her mum, Pam Whynn.
Rachel was 8 months old when she first visited the Mangawhai camp. Now she's 35, with kids of her own. She and her husband, Craig, remember one year when their neighbours kept them awake into the night with their amorous activity, and then loud post-coital critique of their performance.
"Then in the morning, when the children woke them up, they'd complain. If they hadn't been awake so late it wouldn't have been a problem."
Pam says old-fashioned tents tended to reveal more than they should.
The old-style brown stripey canvas sides and green roof used to turn quite transparent at night when a light was on inside the tent. "We got a show one night."
Murray Smith reckons living cheek-by-jowl has become more of a problem over the years as campsites have become smaller. One year, he had to draw up a scale plan to make sure their camping paraphernalia would still fit in the new, smaller sites.
Vehicles that navigate between the sites at speed are also a problem.
• Brown says: It's important to respect each other's space. "You have to compromise when you're living close to a lot of people. Don't wander through other people's sites."
Unlike almost any other holiday accommodation, those in a campground are sharing toilets and shower blocks with strangers for weeks on end. Treating them with respect, and exercising the kind of hygiene you'd expect at home, ranks highly among campers' concerns.
Noela Gunson, who runs the Mangawhai Heads Holiday Park with her husband, Richard, says incidents in the toilet blocks are few, but when they happen, they are memorable.
One year, someone was throwing faeces around the toilet blocks every night for three weeks. "I was coming close to locking myself in there and trying to catch them ... I'd have rubbed their noses in it."
The culprits were never found, but the problem has never happened again.
Park owners clean toilet blocks up to six times a day during peak periods to keep on top of hygiene problems.
Brown says: "What people forget is the sheer numbers you are looking after. At a lot of beach camps it's impossible to control who's going in and out of toilets and showers."
The culprits often weren't even people staying at the camp, he said.
"I've heard of one park where they have keypads on toilets because they wouldn't just lose the toilet paper but the bowls as well. You do hear of unusual things happening, especially around Christmas, but it's not the norm."
• Brown says: People who don't like the idea of sharing can opt for parks that offer units as well as campsites. "They offer the comfort of being in a motel with the benefits of being in a holiday park."
Three hundred campgrounds are members of Holiday Parks Accommodation NZ - these are mostly the more upmarket grounds. They have luxuries such as electricity and running water. There are many others around the country, such as Department of Conservation sites, that offer fewer amenities.
Brown says there has been a noticeable resurgence in camping. His organisation's campgrounds record 6.5 million guest nights a year, with 1.5 million of those in January. Kiwis make up 65 per cent of campers.
Liz Smith says camping is the true Kiwi holiday experience, on a budget.
Huge million-dollar beach houses are springing up around Mangawhai yet, down at the bay, people are paying no more than $18 each per night. And they get better views than the holiday house millionaires.
Being able to sit, peeling potatoes for dinner, while you watch your kids play on the beach just metres away is the kind of experience you never forget.
Liz's friend, 66-year-old Sue Hamilton-Wallace, has been coming to the site with her family since she was 18. "My niece says summers here were the best years of her life."
