You would do well not to follow your intended course of action. Spiking humidity will do nothing save open your crop to bud rot and other molds. In the final stages of flowering, you want to keep your humidity in check at all times or it could end in disaster.
Mites are not affected by temp spikes or humidity spikes - at least not in the short term. You will likely do more harm to your plants than you would to the mites. To combat mites effectively, you will want to look into miticides, and other topical remedies. I would caution the use of any pesticide close to flowering - you are better off living with them at that stage than to do something that would result in something potentially harmful to yourself.
There is a ton of info on the forum on how to deal with mites at certain stages. Read up and you will see that its not the end of the world - just somethign we all have to deal with at some point or another.
