Hello and welcome to Frog Forum! By your user name, you probably have Fire-bellied Toads. If this is the case, you could simply create a more aquatic environment for your frogs. FBT need more water than land. Mine are housed in a 3/4 water and 1/4 land enclosure. But you could do a 2/3 water and 1/4 land. If you can provide them with an environment that is semi aquatic, you will not have to use foggers (the Exo-Terra one is terrible by the way. If you ever invest in one, my experience with the Zoo Med Repti Fogger has been more positive) nor will you have to worry about keeping the humidity up when on vacations.
I like you live in a cold, cold city (Montreal). I use a heat pad (and heat cables) under the tank, attached on one side of my vivariums. The great thing with heat cables (or heat pads) is that it will not dry out the skin of your frogs, like a heat lamp may do. If you do have plants and if they need some sort of lamp, you can get fluorescent bulb (the Repti Glo 2.0 Full Spectrum by Exo-Terra for example, which your plants will love because of the 6700K it has). The lamp shouldn't be on for more than 10 hours a day.
If you need example of fire-bellied toads enclosures, here are some on our forum. If you need more help, feel free to ask any other question:
Cheri's fire-bellied toad vivarium (moderator).
Fruitloop's fire-bellied toad vivarium.
My own fire-bellied toad vivarium. Mine has completely changed. I've replaced all fake plants with real ones. But it will give you an idea of how much water you can have.
Eric