try sending 'daddy' messages to heaven tied to a floating lantern (the ones that fly by heating the air inside with a flame from a firelighter block) or tie the messages to helium filled balloons and let go in an open space outside.

another way of explaining death and heaven stuff to a child is to explain that ta person is made up of bits you can see ...their body, and bits you can't see, their love, feelings, thoughtts etc. once the child understands this move on to ..when a person dies God only takes the bits we can't see up to heaven and leaves the bit we could see for us to bury /cremate or whatever because that is the broken bit. once the bit we cant see gets to heaven it is either given a new body or floats around watching over us, whichever you think is most appropriate, in this case i would probably use the floating around watching over us one as it can then be explained that daddy can't come back because he has no body!and leave it there until the child processes it and asks the next round of questions.