It's old news by now: Childhood obesity rates have been steadily rising these last few decades. Despite heightened efforts to change the nationwide situation, children still engage in less and less exercise with each passing year and are therefore suffering the consequences, which range from diabetes to mental health and body image issues later in life.
For this, one can blame the high-calorie diet that's readily available to every household. One can also blame the ever-growing popularity of gadgets and virtual applications that are designed to glue children (as well as the adults surrounding them) to their beds and couches seemingly all day, every day. Or, one can blame one's own modern values that allow people to equate lax parenting with good parenting, despite all evidence suggesting otherwise.
While it is true that today's technology has far-reaching mental and intellectual benefits and that children's early exposure to it can only benefit them in the long run, it does not mean one is justified in neglecting the development of their bodies. A healthy body paired with a good mind makes for a balanced, well-functioning adult. Which begs the question - how does one entice an entire generation raised by the Internet to let go of their modern toys and engage in physical activities at least once in a while?
First, you as a parent will have to build rapport with them. There's a good chance these children don't know that consoles, tablets, and WiFi have't always been around. Tell them about what you did as a kid and try to convince them that you had as much fun in your day as they seem to be having now - maybe even more since, for one thing, you actually know how the sun feels like on your skin as you ran and sweated it out. Not only is that kind of memory something to cherish, you've also benefited a lot from the vitamin D growing up.
Introduce them to playgrounds and arcades - though it's hard to imagine how those became so outmoded that they need to be "introduced" - then, if you have free space in your yard, invest in some of the big outdoor toys that they end up favoring.
For example, climbing frames. There are all sorts of models available online and in major department stores, which is great because you don't need to go out of your way to find one. One of the best sources for high quality climbing frames is Northern Ireland Climbing Frames, they make custom frames also.
Depending on the amount of space you have, climbing frames can be small enough to fit even indoors, or it could be built up into a child's version of paradise. Bridges and walkways, slides and rope ladders help them develop their balance, coordination, and agility, and have pure fun while they're at it - these sectional add-ons to the basic structure (made of wood or sturdy plastic, depending on the children's age and the number of years you expect them to use it) can be made to simulate those digging and mining games they love so much.
If that doesn't capture their attention on the get-go, nothing else might. And if that's the case, you'd have to find another physical activity they could engage in, like a trampoline or some old-school playtime outdoors with other children. Always keep in mind that your investment in their physical well-being today could only give them a much better tomorrow.