Quick frozen breastmilk ? - help!

LO is being baptized today and we want to have a couple of oz. of milk in a bottle just in case he flips in church. I will feed him before we leave, so technically he shouldn't need it, but just in case nothing else comforts him. (I'm all for discreet nursing in public, but I just can't do it in church.....)

So my question is, if I have a couple of oz. frozen (in a little plastic bottle I can attach a nipple to), can I just run it under lukewarm water to thaw right before we leave and give it to him if he needs it? (the service is about 45 min. so the milk would be out for 1-1.5hrs. tops)

If he doesn't take it, I'm fully aware we have to dump it, which I'm fine with. I have to rotate some of the freezer stash anyway.

I didn't think we would need to bring ice packs, etc. as we have no way of actually heating the milk in church...it would have to be semi-warmed here before we head out the door, if warmed at all.