My DS (who will then be 4 months old) is going for his first overnight stay at his aunties who lives approx 2 hours away. I have been expressing and storing BM in preparation but how to safely get it there? We will be driving over on the Sat morning so milk will be used that day and night, DS returing home on the Sun afternoon. Should I defrost at home 24 hours before and transport in cool bag or let it defrost on way in or out of cool bag...??? He does have formula at his 10pm feed so his auntie could give him formula but don't really want him to have no BM for 24 hours but would rather do that than risk breastmilk going off. Help!