Taking place on Friday 31 July, the free challenge must be completed in the 20 minutes it takes to do the roundtrip, starting at the Emirates Greenwich Peninsula terminal.
Entries will be judged by the chief executive of Mumsnet, Justine Roberts, with the winner to be announced the following week. K’Nex will be supplying the materials for the challenge, as well as one of the prizes – a K’Nex 70 Model Building Tub.
The winner will also receive a family ticket for the Emirates Air Line and Thames Clippers, and free entry to the Emirates Aviation Experience.
Roberts said: "I'm on tenterhooks to see what will happen when you put some children, their parents and a bucket full of K'Nex into a pod suspended above the Thames - but I don't doubt that it will be fabulous."
Families must pre-register to take part before the deadline of midnight on Sunday 26 July.
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