This project is taken from our now discontinued Junior Pack. It fits well into such topics as 'the playground' or 'the fairground'

The only difficulty in the project as shown is drilling the mdf disc that forms the crank at the top of the roundabout. This can be replaced by a card disc to avoid this problem.
All wood is 10mm square.
The two dowels are 5mm diameter.
The sides of the seats and the supporting arms are wooden lolly (popsicle) sticks. The holes are best punched rather than drilled (less splitting).

The 'straps' that hold the seats are made from Tyvek, obtained by cutting up waterproof/tearproof envelopes! It was chosen because it is easier for young children to handle than thread - it can be taped or glued instead of tied. (and it won't twist)

The pivot is a dowel rotating in a plastic drinking straw. The straw could be reinforced by rolling paper around the straw to make a stiff tube.
Glue the model to a large stiff card - it will then be easier to hold when you're turning the crank.