If your choice is try hand warmers or nothing, I would think that that would work better than nothing. If you burn wood, the brick idea would be good too. Just make sure the brick isn't too hot. I would also put a towel mostly over whatever container you put them in to help trap the heat in. Just make sure there is enough room for them to breathe, but enough is covered to conserve heat. Good luck and let us know how things go! Hope the little ones are okay!
