"The increased availability of mobile digital devices has had a positive impact on how young people use their free time."
There are many different views that you could take upon this subject.
1) You could say that the increased availability of mobile digital devices has allowed children to increase their academic success, by being able to search for and complete assignments using these devices.
2) You could say that the increased availability of mobile digital devices allows for children to occupy themselves by providing games, videos, books, and other things to provide them with entertainment, a learning experience, and more.
Hope this helps!