one of my kids has done races on/off but plays multiple other sports and stays in good shape, i.e. ran 27 min as a 7 year old. the effort is there during races, but not much interest in training outside of the race itself.
on one hand, im happy that the kid wants to race and run and can actually run a decent 5k (while many kids are out of shape)..and this level of base fitness is good for soccer, basketball, etc.
but....on the other hand the only reason i ever sign up for a race is to race and run a good time. i kind of feel like that's an important lesson to teach and standard to have. ....i treat running like a sport and train for it.