I would second key00's remarks on not using an enclosed case. make a room in your house off limits for your child and put an open rig of some sort in there. These pump out 70C+ air, and in a confined space you'll never get them mining (ie they'll overheat and shut down before you submit any hashes that matter). If you have a garage or a drill, just build http://www.bitcointrading.com/forum/mining-hardware/guide-make-your-own-open-frame-rig/ out of wood. costs maybe $10, and all parts can be found at any hardware store.


I also wouldn't 'dangle' the cards, they need to be secured to something... Since you're interested in litecoin/dogecoin go to www.reddit.com/r/dogemining and follow one of their beginner guides.