Hide their screens
"Why don't you go outside and play with your friends?" - a question that's been asked through the ages to many a lazy kid. My mum used to say that all the time, frustrated that I wanted to lie around on the sofa watching the telly (Belle & Sebastian, Whacky Races, etc) - and that was long before computer games and social media. When you do persuade them to get out of the house, they love it. The fresh air seems to go to their heads.
There are so many things for children to do outside and it doesn't all have to be play-based. Helping to dig potatoes, plant veggies, grow beans. There are loads of places to pick your own fruit, both on farms organised for the purpose, but just while walking the dog, there are often blackberries to be found, even in the middle of the city - and when you get them home and make them into a crumble, it always tastes so much better. There are loads of lovely books about gardens and gardening that help children learn about growing their own fruit and vegetables and in many ways, it's now more important than ever to learn where what we consume comes from, as we all become increasingly aware of sustainability and the environment.