Final answer:
Dicey's plan to convince their grandmother involved them being very useful on the farm, hoping she would see their value and decide to let them stay.
Step-by-step explanation:
The plan that Dicey had for convincing their grandmother to let the children stay involved making themselves incredibly useful on the farm. The idea was to demonstrate their worth and usefulness so that their grandmother would see the benefit in having them around and want them to stay. This plan revolves around the concept of proving one's value through hard work and contribution to the household and farm duties.