My kids took part in the Run Reigate Kids race and really enjoyed it.
The great thing about the race is that it encourages kids to get out running weeks / months before the actual event. A website is provided for them to track their miles, with the aim that they'll complete 12 miles prior to race day. Then on race day, they complete the final 1.1 mile to achieve a half marathon distance in total. Great idea.
The course is within the grounds of Reigate Priory park and finishes at the same place as the half marathon. There was good support around the course. Chip timing was provided for an accurate time.
Each kids race was based on age group but even then, they had to stagger the start due to numbers, which was a bit of a shame as you weren't racing with all the children in your age group but you could check the times afterwards to see where you finished compared to everyone else.
Each runner received a running t shirt prior to the race to run in and a medal and buff at the end.