I'm new to crested's myself, but I am responding with my opinion because I've noticed you have posted this once before and still no response. Besides my crestie, my only other reptile is a boa I've had for almost a year.
The fogger should be fine I would think. As long as they can't get into the housing part. From what I've read you may not want to run it 24/7 as it may get too humid. Keep an eye on it and adjust the time it is on to get the humidity where you want it but to also let the tank dry out a bit during the day because if it stays too humid and moist all the time it probably isn't healthy and can lead to mold problems.
Again, this is just my opinion, please take it with a grain of salt. Like I said I am new to crested geckos, but I've read alot on the different forums here, and the above is a compilation of that and my own thoughts.
Dani.
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1.0 Dumeril's Boa
...Not that the list will end there, got my sites set on a few others... snakes are highly addictive.