Thanks both of you and thank you for the link.
I have first hand experience of this just three years ago when my sons dad passed away suddenly. My son was 8 at the time so understood it better and had many questions about what happened to him, where he will go now and what happens at a funeral, what cremation was etc.. It was easier to explain to him because he was older. But I feel on shaky ground with my step son because he's so little.
We had decided to let go some lanterns with a letter from him attached, just us because we thought it would be nicer for him. But then his mums family came down today and of course they all have different views on this, some think he should go, some don't. My husband feels he has to do what they want, so I told him to eliminate everyone else and think about what she would have wanted and what's best for his son. It's not going to be an easy decision whatever he decides but it's completely up to him. He knows I'll support him whatever, but I don't want him to take him because of pressure from anyone else.