WFH, summer kid camps that did free or cheap activities during the day, friends who also had kids (returning the favor another day), relatives (mine were extremely unreliable), and all else fails paid child care.
My relatives were absolutely useless for childcare. Its fine if you don't want to look after your own grand children, just say so. But under no circumstances repeatedly say you will have the grand children then back out on the last day, many many times.
If their parents are retired they’re Boomers. Considering the levels of “got mine, fuck you” attitude and delusions about how they “did it on my own without help” this doesn’t surprise me at all. Not saying this is the entire generation, there are actually very caring Boomers out there. But in general, it’s a pretty pervasive sentiment of today’s retirees.
On the one hand, I'm lucky that my wife works at a daycare that runs day camps for children up to 8 (my daughter is 5), but we still don't like that she spends the entire summer with strict schedules and things like that, so that for 15 days she goes with my in-laws and 15 with my parents, in both cases they are retirees in very good physical health and eager to play with their grandchildren.
I'm going to assume you are asking because, you are too busy at work like most parents. Luckily the state and town I live in provide (our tax dollars) summertime activities.
Absent this kind of program I would look to an urban league, ymca, or mutual aid program for child care depending on the age of the kids. I encourage you to look for programs like these if you're in a tight spot for childcare.
In my town, most of the summer camps fill up in March. Every dual-income family I know has a spreadsheet and keeps track of exactly when online registration opens. It’s a nightmare, and expensive too.
Mine are starting to get old enough that we are doing a mix of camps and WFH weeks. It’s not ideal but we’ve scraped enough together that it mostly works.
When they were younger, my wife and I basically had to work different shifts, although there were also long stretches where I just worked less(because I had found ways to make good money like so). Once they turned 6 years old, Boys & Girls Club was a lifesaver. During the summer, the kids actually prefered to go there on days we didn't have anything fun planned(nor $$$ for activities).
If on vacation, and a parent to small children, I'm going to assume any responsible parent will not leave their children alone whatsoever, unless the children are asleep in a safe place.
It's "challenging" as much as the rest of the year when not on vacation, in my opinion.
Maybe I'm still misunderstanding or missing something.
Where I live, you get kindergarten basically all year round, except maybe 1 or 2 weeks off. You can also send your kid to kindergarten for 9 hours or more.
But then school comes, they go to school for like 4 hours a day and there are about 3 months of vacation throughout the year.
At that point my kid will be 7 years old and I will have rejoined the workforce. I have no clue what exactly the plan is here.