Hi Luke,
kamilb is not asking you if you have a battery, he's pointing out that you would need a battery.
There is no law to stop you, as a 12 year old, taking part in an event if you use the C5 as a bike. As he pointed out with peddle power alone you would not be able to keep up with the rest of the participants, therefore you would
need a battery. This of course changes the legal situation.
Though I can't see any police pulling a C5 over to check the driver's age.