Busy Board

Activity boards comprise of a base to which is attached a selection of gadgets and Gizmos designed to help very young children, to develop fine motor and cognitive skills, hand-eye coordination and problem-solving abilities.
Many of these boards exit on sites across the internet under the names of Activity Boards. Busy Boards, Sensory boards, in a range of sizes and complexities.

My Busy Board uses some of the same features, such as Bells, Lights and Torches, but mainly it has 3D printed items intended to help young children develop their motor and sensory skills in a fun way. It has nine 3D printed Gizmos not all of which have been included onto this 'Thing' just yet but it does have four that are fully worked out with a description and STL files.

I developed this for my Great Grandson and with his testing, some enhancements have been made and included here.

There are so many items that could be included already existing here on Thingiverse that I'm sure you will have no trouble finding ones that you can use to fill in the gaps that I have left. Things like Marble runs, Clickers and Fidget Spinners.

The Items included here are as follows:-

1- Revolving Teddy bear, this comprises a handle which turns a Teddy Bear model sitting on the top via a pair of Bevel gears. Teddy is easily removed and replaced.
The model I used came from https://www.thingiverse.com/thing:20938 so thank you 'cerberus333'

2- Pop up head, the most complex one has a spring-loaded head that pops up at the press of a button

3- Key with Ratchet, turn the key and the ratchet inside clicks.

4- Coin Box and Stacker, Coins with 3 different shapes cut through the centre so they can be stacked when taken out of the container with a screw on lid.

There is also a box with a button on top that when pressed plays a sound or tune like this https://www.ebay.co.uk/itm/253999530459?ul_noapp=true.

A hand crank music box inside a Printed case like this https://www.ebay.co.uk/i/351238814929?chn=ps

A Bicycle bell, a torch with projector and Tap on Tap off LED light.

I used a Bamboo Breadboard for the base, although other materials are equally acceptable, I also stuck the items to the board using double-sided sticky foam pads, you could screw or glue as well.
Hope this gives you ideas that you could build for your own children or grandchildren.