Rider Switch is mostly for attractions with height requirements that children can’t ride (or that a child or adult doesn’t want to ride).
This is more information about Rider Swap:
https://disneyworld.disney.go.com/guest-services/rider-switch/
You will be able to hold your child on your lap for shows. You will probably want to hold your child in shows so she can see better.
For many rides without height restrictions, you will be able to hold a small child on your lap.
Winnie the Pooh is an example of an exception because of the ride car motion - during the Tigger parts, it bounces. During other parts, your honey pot floats, bobs, or follows the motion of what is going on in the scene around you.
Peter Pan is one you will probably be asked not to hold your child because of being high up during the ride.
Pirates is also probably no because of the drop.
If in doubt, ask the CM.
My daughter with CP is an adult now, but we held her on many attractions. Also, even though she coukd not sit unsupported, many ride cars easily held 2 adults and one child. With her seated between us, we were able to give her the support she needed to sit up.