I have mine growing in 10% humidity, Terrariums aren't needed. Depending how they came, they still need to be hardened. So you can place the pots in a large container, keeping the soil very moist by sitting them in a water dish. Mines can tolerate basically having their root wet.

Now to hardened them off, place them in a large container but with small opening. They will be in shock but once they start to perk up, which may take up to 2 weeks, crack the lid a little to allow some humidity to escape. Keep an eye for wilting.

Once they get accostomed, open the vent or push the lid off a little more. Again checking for wilting.

It shouldn't take more then 2 weeks for them to be hardended, cape sundews are very sturdy & good for beginners.

One thing, did the sundews came in pots or bare root? If they came in pots, they should recover even quicker. Black Jungle sell their plants somewhat hardened.

I bought from them 2 potted N. rafflesiana "white spotted form". They got used to my conditions real quick. But being lowland, they require more humidity then the highlands.

They did come in small pots. This morning some of the leaves on both of them grew their dew back.

Well when I turn the lights off in the terrarium the humidity lowers to at least 65%, when turned back on, it can go to 80-85%. They don't seem to be wilting though.

Do these look fine to you?
{{gwi:545198}}
Sorry for the crappy quality :(
{{gwi:545199}}
{{gwi:545200}}
{{gwi:545201}}

You don't need to go out of your way to provide humdity. Just putting the pots in a plastic conatiner or water would be sufficient.