Smartphones have made it easier for you to check work emails and messages even after you leave the office, but this doesn't mean that you should allow yourself to do this all the time.
Make it a point not to bring work home with you. This way, when you are with your children you will have no need to constantly check your phone for correspondences.
If you work from home, on the other hand, set a clear distinction between time for work and time for play, so that your attention is not divided between the two.