How do I help make my child with a Vision Impairment feel more involved with the sport that their sibling does?

Depending on the sport or activity you could do things like walk the course with them beforehand, let them explore the equipment and how it works. Find out if audio description is available or provide your own version, so they can feel more involved. You could also find out if there is a VI group or club for the same sport that they could join to experience it for themselves.