I've been fascinated by the mystery of children with this disease for 6 months. Epidemiology is outside my area of expertise but I'll state my case whilst I'm bored on a holiday.
The observed differences in Sars-CoV-2 transmission between children and adults can be predicted making these 2 assumptions:
Using these assumptions, the following applies:
Spread from children (either child-->child or child-->adult) will be via upper mucosal secretions (via droplets and surfaces). It will not be via aerosolised virus. Super-spreading events will not be possible. Disease will be more often mild or asymptomatic (virus within droplets or via fomites will generally be deposited in oral and nasal mucosa, and less likely to reach lungs)
For adults, the situation is different. Lungs will frequently carry a significant load of virus and transmission events will be far more frequent due to aerosolisation and dispersement of virus. Virus will often travel direct from host's lungs to receiver's lungs and the cycle goes on... Super-spreading events will be possible and disease will more likely be severe on account of the lung involvement.
also predicted with these assumptions is that "viral loads" (as measured on pharyngeal swabs) will be the similar between children and adults (infectivity however will be very different)
(It's almost like children should be regarded as a different species to this virus!)
I'll shut up now.