It may not be very easy to wean away children from the gadgets and playthings they are use to and habituated and in which they find pleasure.
The first and foremost is to set an example. That is, the parents should themselves keep away from the gadgets mostly or at least on prime times of meals time, family time and kids' study time.
Parents should spend more personal time with their children. They should (at least one of them if both are working) give first priority to talk with the children immediately after returning from work and fleshing up. They should ask how the day went in school, about friends, their play and play time, about any homework or any communication given to convey to parents, about exam schedule, etc etc. They should also ask if the food given to them was sufficient and tasty. whether they are okay physically, (like how is the headache, leg ache now etc.). They should enquire about what interesting thing happened that day etc.
Once that is over the children may be given some time to play outside, if it has no become dark, or inside the society ground with friends or siblings. Parents also should spend sometime to play with them as per the children's age and interest if possible. Parents should sit with the children, at least to some extent when they are studying and help them in clarifying their doubts and narrating some personal experience examples to enhance understanding of the concepts. Parents should take their children to visit relatives, friends, and also visit tourist places on holidays and vacations. Children should be taken with them in social events.
Parents should not put a sudden brake or halt to the use of gadgets, but slowly earning them away and allowing the use for essential and positive uses. They should be encouraged to participate in team events outside
Once the children know the optimum balance with outside world and in house gadget use they will be okay.