Drop the fate of the world part. I think that's the best of this series.
Allthough children's card games are pretty silly (yet can be entertaining) they can't really be much more than something that you kill time with (much less save the world).
Motorbikes have some degree of competitiveness and even major world race tournaments/leagues. Throw that and card games together and you have something similar to chess boxing (google it up, it really exists).
It's something so stupid and awesome it actually is believable.