Stock paper, construction paper, paper plates, string, and crayons are all one needs for a project.
For the aquarium you need boxes, either several shoes boxes or one large one.
I prefer crayons over felt pens; they last longer and have more colors.
Index cards are good to have for the word games, if you don't feel like
cutting pieces of paper.
A paper-cutting board can save a lot of time.
For a performance
Garment racks covered with material are very practical to create a stage. They are lightweight and easy to store. Place several - as many as you need - side by side for the backdrop, and one or two on either side of your stage.
It can have windows and become a puppet theatre.
Do not put the wheels on for the stage racks, but you can roll racks onstage for a specific scene.
Place sandbags along the base of the stage racks.
If the performance is for older (taller) groups, place poles that fit into the side cylinders, to add height.
Puppet theatre on one rack.
Puppet placed on a chair.