Spasticity is usually caused by central nervous system injuries, such as brain injuries or spinal cord injuries. Spasticity is a little different from stiffness.
I have cerebral palsy spastic diplegia. So it affects my legs and sometimes my fine motor skills. I walk with two canes. I do things a little slower, but I get things done.
One thing that parents can say to start a conversation with their kids is, "Let's talk".