Avrah,
yes, chromebooks are also good solutions.
on opendns, you can disable wifi and just use ethernet cable to the router. You can use glue and nails to make sure the computer is not going to starbucks – unless you live near one. Talk to your neighbors not to use 613 as password to their network.
On any computer, you should always have an admin account controlled by parents, and you can install all kind of family control software in that account. As I mentioned, maybe the most fool-proof would be to get screen snapshots every several minutes and then either quickly review them or run thru some recognition software. You can probably write such software in one hour if you don’t want to pay $20 for shareware.
But my point about related issue is not a substitute for filters, but it is important not to just focus on filters.
There are these reasonable instructions on how to use electronics in the house, and these should be distributed to all parents and repeated multiple times. It is very suspicious that TAG is not mentioning these: either they are vested in their digital solution, or they do not look at the problem at large. In either case, this does not inspire confidence in their professional judgment and business model. I think interested people should talk to them and ask questions.