Does he read your emailing more often than he does calling you or emailing? I would suggest when he reads it have him hit reply back... to let you & the kids know he ok! tell him it doesn't have to be long just a short reply.Your worried about him
The ony thing you can go do is to keep encouraging him to call you and write you more often .
My dh kept in contact with me often just to let me know he's was ok..I can understand your fear ,sadness & angry that your dh is not contacting your more often..You can't make him do it but I would definetly would give him a good talking to him when he gets back if his behavior doesn't change