A Hawke's Bay family was left in awe after a stranger approached them inside a McDonald's and handed the two children a $50 note each before disappearing out of the store.

Amanda and Dave McIntyre were at the McDonald's in Taradale with their two boys when they were the receivers of a random act of kindness.

As the couple sat with Ben, 8, and Liam, 11, waiting for their food, the boys kept themselves busy playing with their Rubik's cubes.

A "lovely lady" who had been eating at a nearby table approached theirs and stunned them with the kind gesture.

"She approached our table and told us that it was a joy to see the boys playing on the cube rather than on a device," the boys' mum recalled.

"The lady asked if our boys had KiwiSaver, I explained that they didn't have KiwiSaver but they had savings accounts. The lovely stranger then took two $50 bills out and gave them to the two boys," she added.

The mum said she tried to encourage the lady to take her money back but she refused.

"We sat staring at her gift shaking our heads in disbelief. The lady said this is to start a KiwiSaver account. She looked at our boys and told them to tell their parents to look into compounding interest and, with that, she was gone."

The four were left "gobsmacked" and trying to process what had happened as it all took less than a minute.

"I suddenly realised we had not thanked her so I yelled out 'thank you' as loudly as possible. She smiled and waved from outside. I ran to the window of the restaurant to wave out and mouthed 'thank you' again but she wasn't looking," Amanda recalled.

The mum says the whole family feels grateful to have found themselves on the receiving end of such a kind act.

"We just looked at each other in disbelief shaking our heads. We waited for her to come back and tell us she had made a mistake. It was too big to process," she said.

"Ben said thank you but I don't know if she heard and Liam was worried she had given us her grocery money and, as is typical of Liam, he hoped she would have enough money to get her groceries."

The mum says her only regret is "that we were not quick enough to express our true gratitude to her".

"It was such a sweet and kind gesture and we are so grateful that our boys were able to experience being on the receiving end of someone else's generosity. We have spoken to them about paying the kindness forward in the future," she added.

Amanda and Dave are going to speak to their bank this week about starting a KiwiSaver account for the boys and will match the amount they received from the kind stranger.

Speaking to the Herald the day after the random encounter, the mum explained the two boys love their "old school boredom busters" and Liam is particularly proud of his Rubik's cube skills, with brother Ben trying his hardest to follow in his big brother's footsteps.

"Liam deciphered the Rubik's cube about a month ago. It is now his favourite toy, and let me tell you, he has made a pretty penny from that cube," the mum revealed. "His friends see him playing with it and, of course, everyone knows how difficult they are so no one expects him to be able to complete it, so people think it's a safe bet to say I'll give you some money if you can complete this. His Aunty Ashleigh owes him $10 and his friend handed over his change as well."

Whenever the boys are out with their parents and have some idle time waiting for food, they tend to take books, word searches, sudoku puzzles or playing cards as well.

The proud mum explained the boys love those types of brain puzzles and added that they "absolutely" get their device time as well, but only as a treat, from 3pm to 4.30pm on Saturday and Sunday afternoons.

"If Liam didn't have the help of his device and YouTube, he would have never learned how to master the cube. But now that he has mastered it, he take his cube wherever he goes."