Sorry for your loss, OP.
I lost my dad in 2018. It too, was a surprise. The only advice I can offer is not to run away and hide in this time of exceptional grief. Be strong, embrace the reality of the situation and how it's about to impact you and your family. The pain is the pain and you can take solace from the depth of feeling his loss provokes in you, as it proves the strength of your love and your bond. It doesn't lessen the pain, but you will feel better dedicating your energy to family things as much as possible. Spend time with family you don't see enough of. Try to be a hands-on participant in the arrangement of the funeral, even if that is not your assumed role - I arranged pallbearers to be a mix of friends and family, and wrote some words. It helped with the feeling of idleness, as so often in grief you feel like everything you do has been rendered pointless and meaningless by the magnitude of losing someone. Your life is going to be trapped inside the orbit of this grief for a while, so the best thing you can do is accept it, stay busy, don't block out your feelings, and be a rock for other people. Do things you know would have made him proud. Time will do the rest.
I don't have children, so I don't know how you explain that kind of thing. I hope it goes as well as possible.
