I don’t like it, but imho it’s a reflection of an architectural flaw of Lemmy.
The fediverse should have distributed channels. …but “distributed” doesn’t need to mean, every channel sits on an isolated instance/island and the only way to share a message between instances/islands - is to duplicate content.
A better solution would be that channels would be globally unique (ie there would be just one “til” channel). People would subscribe to it, and each instance would be the “custodian” or keeper of their users comments and posts. The “custodians” could/would moderate their users posts and could “defederate” from other instances (if they don’t like how others are moderating their users).
This would avoid situations where one channel gains popularity, but the instance closes shop and the fediverse is left scrambling to fill in the gaps.
Treat the laptop as a desktop and put it in a public space (ie: the livingroom). Meaning gets an external monitor, keyboard or some other reason that it becomes a stationary PC.
Then an adblocker or pihole will be fine. Then have a discussion with your kids, that there are some very ugly places (use death/gore/animals being hurt, etc) that are not suitable people their age (or even your age)… and this computer tried to monitor and block it.
This won’t stop curious kids from being curious, but they will understand why the guardrails exist… and having it in a public space will avoid leaving them alone in their personal space with the untethered internet at their finger tips.