When are you going? If you've got a few weeks, could you withhold misting a day or two to see how they do? You'll hear from more knowledgeable than me, but the plastic bag makes me nervous! I do like the north facing window idea.

Are you traveling on day one, gone on day two, back on day three? Probably not.

I wonder if they really need misting every day at this point. Do you have a friend or neighbor who might be willing to babysit if they truly need the misting daily? (I will!)

...and commercial cactus soil could be more water retaining?

How long are they out from the humidity tent/ziploc bag? If you put one on, it probably doesn't need any extra starting humidity (I am assuming you want to add some extra moisture to create that).

Since you are misting top of the soil, perhaps a wick would work? Not sure how much they will dry out in 3 days...

Thanks for the replies. I was basically gone on the morning of Day 1 and just came back on the evening of Day 4. I ended up using the plastic bag method with only slightly damp soil.

No one near could have come over to mist them :( But I am glad to report that they seem to have survived the ordeal! I didn't see any mold on the soil, but there's a tiny white spot on one cacti so I'm not sure if maybe I got them out of their improvised greenhouse just in the nick of time. Hopefully that one will recover anyway. I actually have two new babies that appeared during my absence. They're back in a sunnier spot now.

Very good. Thanks for the update. It's always interesting to hear the results of the various situations.

pics?