You're overthinking it again, getting circular in your process. Breathe, you're just growing plants.
I assume you read the thread about refrigerator dormancy that detailed a very good process, otherwise I don't think you'd have brought it up. If not,
refrigerator-dormancy-t36505.html
The title of this thread says you have concerns about it as well, so you've asked about and have been given some very feasible suggestions and examples of methods that will work in your area based on your description of what you have available. But you and your family have real concerns and fears regarding potential issues with those. The likelihood of those issues actually happening are, in reality, very low, but the reasoning behind the thoughts against them are solid.
That greenhouse you linked could work, but it only provides frost protection, not freeze protection. You would still have to find a way to provide heat to prevent freezing, and the easiest way to do that is a space heater. I don't think a heating pad would be sufficient for that volume of space. You could design a complex Goldberg machine that connected the enclosure to house heat, complete with a chain reaction of louvers, fans, lights, bells, whistles, and something to do with a monkey, that would only occur when a certain temperature is reached, supplying just enough heat to it to keep it above freezing. However, other options are much less expensive than Purina Monkey Chow.
Last, and I don't say this lightly, if the basic care of these plants is causing this much anxiety and concern for you, perhaps temperate carnivorous plants aren't the best choice for you at this time. You have some subtropical ones that can stay on a windowsill year round, maybe focus on those until such a time in your life comes around that you have more options as to how to provide conditions conducive to the more needy plants.
Everything happens for a reason. Sometimes the reason is that I make bad decisions.
my-freeloader-list-um-er-grow-list-t40190.html