Maybe grandpa was ill or had signs of his next life, which was mentioned by his family, or you found out, so you made up those scenes in your dream. Maybe you want grandpa to give you some life advice, but in reality you may not. You are eager to get it in your dreams. As for food, it is human nature, and it should be a coincidence to call in the middle of the night.
I dreamed of giving you RMB because I wanted to get some valuable inheritance or other things from my grandfather. It shows that you admire his old man and miss him very much.