Children's book illustration live brief from client

i was contacted by a mutual friend about a substantial commission to create illustrations for a children's book he plans to publish to commemorate the passing of his grandfather (who wrote the story).

i was really humbled by this and excited as i have never been approached for a project commission before!

what client has clarified to me so far about the brief: 
 I'm not time specific, so if you need it for uni work you can do it to suit you!

It's a story my grandfather made up and used to tell me and my brother and sister when we were little, and after he died we found a version of it written down  when we cleared out his house, so thought it would be nice to get it published. 

the story summed up: 

 about a kingdom with a princess etc, and up on the hill near the Kingdom lived a big dragon. The king said to every knight in the kingdom, which ever knight kills the dragon can marry his daughter, the princess. All the Knights try but all get eaten or killed by fire etc

A tramp then asks to have a go, so the King laughs at him and tells him to go ahead, thinking he will be unsuccessful. He gets a giant toffee apple and wheels it up the hill in a wheel barrow, the dragon eats it and it gets stuck in its throat, so it can no longer breath fire! The town are saved, the tramp can now marry the princess, and they all lived happily ever after.

thinking about process to create the illustrations in: 

I asked the client if he could clarify the style he would want me to produce the illustrations in as he mentioned he had seem work of mine he liked - hence why he wanted me to illustrate the book. so he liked a few styles on my Facebook page he would like me to experiment with for the illustration; 

As this is for a potential published book, I plan to ask my ppp tutors John Watter or Fred bates about how I go about copyright, loyalties etc