Organisers have talked to emergency services and local authorities (for clearance and to get guidance on safety). IIRC Clapham is still closed off and being treated until a crime scene, certainly until at least late morning, but cleanup is underway at the other sites. And it's expected that there will be a need for more cleanup at the private shops and businesses once they have had the insurance loss adjustors round, so likely to be an ongoing process.
If children already know what happened / saw news footage I think it could be helpful, and also show them community pulling together for something good / that most people are kind and helpful.
I would go but not sure it will be practical/safe with baby in sling and don't have anyone to leave DD2 with. Also local site is Claham which (as above) isn't ready for cleanup yet.