Updated: Jan 12, 2019
When looking for a fine motor activity LEGOs are a perfect medium. They combine motor planning, bilateral control, visual perception, as well as hand and finger motor intensity for building strength. A great way to extend the fun is with a Makey Makey. With one base design your client can customize it to play it as a game controller, piano, or sound effects machine. Playing any configuration requires isolated controlled finger movements, but playing with the game controller build allows the natural consequences of gameplay. In the videos I'm mostly using one finger, but you could have your client set one finger on each key to play. I would recommend some dycem as the LEGO base moves easily.
Try out the build guide. View the video some examples of how to use it.