Hello Jack :)
Here are my suggestions, and I hope they're helpful. They are some small adjustments that you can make that don't take a lot of time, but will definitely make you a good AND responsible father! :)
* SMILE at your children - giving your child the impression that he lights up a room when he enters will change who he is! It will affect who he becomes as an adult. It can make the difference to his career choices; financial health; physical, emotional and mental health; relationships - in fact that one adjustment could make his life a success! How you react to your children will have more effect on them, than how often they're with you.
* During the time you do spend with your children - make sure you're really present. BE there. Listen to them, allow them to speak to you, even if it doesn't seem to be particularly interesting or relevent.
* If you can, try to make some special time (even if it's only half an hour once a week) with each child, during which you do something with them, that you only do with that child - an activity, reading a book, playing a particular game - whatever it is, it'll be something that child feels is special to him/her.
* Laugh - humour is magical. Share humour with your children when you can - especially during moments that may otherwise feel tense or stressful.
* Show kindness and warmth along with firmness in discipline.
I hope this helps.
Enjoy the time you do have with your children. :)