If I were you and it was possible to get handwarmers I would probally take your kids pee. All you do is put it in a small container (maybe a pill jar) put the handwarmer on it for a at least a half hour (like the ride over or what not) and it should come to temp because you could be taking a risk with all those supplements. Just wanted to offer you another idea if you were feeling unsure. Well best of luck!!!!!!!!!