Yes....that should work, though you may need more than one depending on size of container and sachet....I'd do what betteirene suggested with the candy in the container as a test.....it's heartbreaking to lose the sugar work you've done.

I could use a sachet of silica gel maybe?

If your home is too humid you could also them in a container with Damp Rid in it. Just make sure the sugar and Damp Rid don't touch.

If you can keep them away from humidity, you can, especially in winter when indoor air tends to be dry as the Sahara.

Sugar is hygroscopic and attracts moisture. Place a piece of unwrapped hard candy on a saucer overnight: if it isn't tacky or sticky in the morning, your home is dry enough to make spun sugar in advance. If the candy is sitting in a slight puddle, however, don't make the caramel until a couple hours beforehand.