Well, sort of. Much of TCP itself can be done for anyone, even without status - it's just a linking of PNRs.

In the vast majority of cases this has absolutely no additional benefit - neither the airport staff nor the cabin crew will look at it, likely even when prompted. It doesn't bring any baggage or IrrOps benefits. In this case though, where you want a contact centre agent to allocate a seat under the child policy, it might well help to circumvent a few questions and smooth the process.

The Gold benefit, which has no relation to the child seating policy and occurs manually, is the free allocation of seats on the same flight/in the same cabin.