Even so, the digital craze has subsided somewhat compared to a few years ago, according to expert Thomas Feibel whose office for children's media organises an annual German prize for children's software.
"The variety of apps on offer is currently a frenzy, but slowly fatigue is setting in," he says. "The time of the really big innovations is over."
That may be because everything has already been created. There are already so-called augmented reality books in which children use a smartphone camera to search for hidden content and little surprises.
Even board games have moved on to smartphones. And older kids can use apps to control and steer electric toys.
Such ideas are currently very popular, Feibel says, not just with toys like racing cars but also drones.
"They are often ingenious things, but admittedly often also very expensive," he says. Much cheaper or even free are apps for kids that don't require accessories. However, here the question is the range that's offered.
"Finding a good app by sheer luck is very difficult. You need to look around a bit and do some research," says Martina Holler. Together with her colleague Felicitas Haas, she reviews apps suitable for children and adolescents on her blog. Bloggers can be found round the world offering judicious reviews of apps, whereas the recommendations on the likes of the App Store and Google Play are of limited value to parents, she says, as they typically recommend too few apps or else the same apps all the time.
Which is a pity considering the tremendous diversity that's out there.
"There are apps for playing and learning, there are puzzle apps and classic children's books," Holler says.
"A good app, for example, exploits all the technical capabilities of the tablet or smartphone," she says. "That's funny or cool for kids and gives them more desire to use it."
Parents should also take care that apps don't bombard their children with advertising or in-app purchases.
"Free apps often finance themselves in that way," says Holler. That's one reason she recommends paid apps: "While there are also good free apps, paid apps are often better." Paid apps are not expensive either - six euros (6.70 dollars) is for most the highest-priced category. According to an initiative in Germany that focuses on media use by children, kids aged under 3 years shouldn't be using mobile devices with apps on them at all. At that age it's more important to engage with the real world, the initiative recommends.
There's nothing wrong with a few virtual adventures, but not for longer than 30 minutes a day and parents should supervise them.
As children get older, parents can let them use mobile devices for longer and by themselves - but after activating parental controls and child-protection settings.