If it is muktza to the owner who is rich, it is muktza to a poor person to use also.

Chapter 309 Section 1

A father can carry his son in a private property, even though the son is holding something muktza as the child has gaaguim [tremendous love] for his father and might become ill if he is put down.

Chapter 309 Section 2

A basket that had a hole and was filled with a rock, the rock is not muktza.