This animation is lovely!
I love the story and the character designs.
I believe that the buttons menus deserve a suitable background, instead of it being blank.
If you wanted to add more to this creation, I would recommend adding sound and colour.

An example of sounds that can be used are:

Crowds - People talking and walking/Children laughing
Roller Coaster sound effects
Circus music...

The objects they interactive would include the sounds that they need such as:

The bouncy castle deflating
The Cotton Candy machine...

But overall, I love this animation and I would love to see these characters developed and used.