Over a relaxed supper at a friend's house the subject of holidays comes up: why not spend a fortnight away together? Good company would be guaranteed, the children could enjoy pals around the clock, and chores and costs are shared.
During the mornings the men could play a round of golf together and on their return the mothers could disappear to the spa for a well-earned break. Best of all, you would have trustworthy babysitters on tap for the odd romantic dinner out.
It sounds perfectly idyllic, but going to an unknown space, in a foreign country with a possibly unfamiliar language, can result in a huge amount of pressure and stress. Increasing the numbers of people involved can just complicate things further.
"Holidays tend to be more stressful than people ever expect," says Linda Blair, a clinical psychologist in the UK. "In your home environment you're relaxed and can accommodate other people. Somewhere new, you concentrate on meeting your own needs and you're much more sensitive to people getting in the way. There are so many potential explosions."
For a multiple-family holiday to be a success it is important to have a chat about expectations before you go.
"Clear communication is essential, otherwise a shared holiday could destroy relationships," warns Dr Anu Sayal-Bennett, a consultant clinical psychologist who works with expatriate families in the UK.
Discuss how you want to spend your time - are you sun junkies or mad about historic ruins? If you agree to do your own thing from time to time before you go away, no one should feel snubbed once you're on holiday. Set some ground rules and consider your different parenting styles and whether there are any potential clashes.
It's also worth talking through the basics, such as who will do the food shopping, who is going to cook, and if you'll split restaurant bills down the middle.
"Acknowledge that it will be difficult at times and this will make it easier when tricky occasions do arise," says Gaynor Sbuttoni, an educational psychologist in the UK. "Talk about the fact that the children will play up and discuss how you want to deal with it. For example, are you happy for other people to discipline your children?"
Despite any pre-holiday meetings, going away with other families will still entail a certain degree of adapting and accommodating.
"If something niggles you, don't ignore it otherwise resentment will build up," warns Sbuttoni.
If your children are not allowed to watch hours of television, or to play violent video games, you'll need to find a middle ground if your friends' approach is more laissez-faire. When it comes to bedtimes, it's a slightly different matter.
"You know your child and if they can't cope with going to bed late then you need to explain that you can't go out in the evening," says Sbuttoni.
It's worth considering separate accommodation, such as holiday chalets next to each other, so you're able to retreat at the end of the day.
"Teatime in my house is rarely a pleasant affair," says Sal Gilbert, a mother-of-three in Abu Dhabi. "Everyone is exhausted and it's simply a case of getting through until bedtime. It was one of the reasons why we hired separate villas when we went away with friends last year. It worked out a bit more costly, but it was worth every penny when it came to our sanity."
The children are bound to fall out at some point and it will be a disaster if the parents always side with their own offspring. To avoid this, Sbuttoni suggests you ask each child in turn to explain what the problem is, how it makes them feel, and then get them to think about a solution. "If you approach a falling-out in this manner, you can avoid anyone feeling like their child has been over-disciplined," says Sbuttoni.
"I didn't realise until I went on holiday with my best friend that we had such different parenting styles," says Anna Mitchell, a mother-of-two in Dubai. "She believed in letting the children fight it out, but I just couldn't sit by and let that happen. On the second day I raised the subject and we agreed to intervene whenever things looked like they were escalating between the children. I'm so glad we had that chat because I'm not sure our friendship would've survived the holiday otherwise."
Despite the challenges, there are plenty of ways in which you can benefit from a multi-family holiday.
"If it works it can be brilliant, there are a lot of learning opportunities involving cooperation skills and negotiation," says Sayal-Bennett. "If your children get to see you working through conflict with your friends in a grown-up, respectful manner, they will learn a lot from this."
Joint holidays can be a particularly enriching experience for an only child, who will have an opportunity to enjoy companionship while learning how to accommodate other people.
But with so many potential pitfalls, holidaying together is not for everyone. "Some expat families get addicted to being with other people all of the time, while others see holidays as a chance to take a breather," says Sayal-Bennett. "In many ways, expat families might be more experienced at holidaying with others and their expectations might be more realistic."
But for all the families out there who have tried it and sworn "never again", think carefully before stepping through the travel agent's door together.
The survival guide
• Consider whether the children are likely to get along. Just because parents are friends, doesn't mean the kids will automatically click.
• Agree on boundaries before you go.
• If possible, consider taking an au pair or helper along. An extra pair of hands can make all the difference.
• Spend some time alone as a family every day, and be sure to have your own space to escape to.
• In shared accommodation, more than one bathroom is essential.
• It's better to holiday with good friends with whom you can be more open, than to risk it with a family you don't know very well.
• Consider overlapping – spend one week with your friends and one without.
• Take a weekend break with the other family to see how you get along – before international flights are booked.
•Think about waiting until your children are over five, when they will be more flexible and will love having playmates.