Please provide a citation in the NRCoT that a child travelling as per the rules, without a ticket, cannot have a seat reservation and is not entitled to sit down.
3.2:
The gateway to Britain's National Rail network. A portal into UK rail travel including train company information and promotions; train times; fares enquiries; ticket purchase and train running information
www.nationalrail.co.uk
3.2 Some types of Ticket (for instance “advance” Tickets) require you to make a reservation when buying your Ticket. For other Tickets you can request a reservation either when buying a Ticket, or before the departure of your train on presentation of a valid Ticket, at most staffed stations. You are allowed a maximum of one seat reservation per person for each train that forms part of your journey.
It is not possible to present a valid Ticket for someone who does not hold one, so a reservation should not be issued for them. That LNER's website has a poor way of verifying that that actually just verifies that you entered a number that isn't 0 (and that GWR's site doesn't verify at all) doesn't change that. Once it's technically possible to do so I'm sure they will, it just isn't with CCST.
It looks to me like the stipulation regarding not occupying a seat if required for a fare paying passenger may have been removed as I'm struggling to find it. It certainly used to be there. Does anyone know when it was taken out, perhaps when the NRCoC became the NRCoT? Or am I missing it?
This being the case the original poster needn't worry about a "dodgy" reservation as it would appear there can be no penalty for it. And with LNER having a high proportion of reserved travel I bet there's worse misuse of this system, e.g. people 'blocking" the other 4 seats at a table in an attempt to keep it for themselves.