> books are fine once you hit 6-7 years old, before then they'll get bored of them after 15-20mn since they can't read comfortably

Teach them to read young, buy books that are active, etc. My kids could read for a lot longer by that age, and so could I.

> in places that aren't adapted for children (e.g. in an airplane or train), a tablet can be a life saver

Talk to them, play games with them....

I loved spending time with my kids, and now they are grown up I am very glad I did.