I miss him. I think about the way we all picked apples together. After a while, I won't cry so much anymore. This shows your children you're human, reassures them, and also gives them the room to express the things they miss about Grandpa, too. Differentiate your concerns from those of your children.
Adults think differently about life changes than children.
Adults think in broad terms and are able to make long-term projections. Children primarily want to know how the change is going to affect them right now. Reassure your children about what will happen to them. Children interpret experiences in terms of themselves. She will make your meals and read you your stories.