Test to release for under 4s

I am planning on using the test to release scheme for a trip to England at the beginning of August. I am a British national living in France, double jabbed with Pfizer. I will be travelling with my 3 year old child, also a British national living in France unvaccinated. Does my 3 year old also have to opt in for the test to release scheme or is he exempt from quarantine requirements? He is exempt from testing upon entry into England because he is under 11. I cannot find any information on whether he is also exempt from quarantine. I cannot find a test to release provider that tests on under 4s. This suggests to me that he is either: exempt from quarantine altogether or he has no option but to do the full 10 day quarantine. Thanks for any responses.