Transferring Breast Milk

I have to travel up the coast in a few weeks for an important appointment that goes all day and I can't take my daughter who is breast feed so she is being looked after for the day. I'm worried I won't have enough time to express enough for her as it takes a long time for me to fill a bottle, so I was wondering if I can express and take it with me in the car. But the drive is about 10 hours. Has any one transferred milk before. If so how did they do it? In an eskey with ice? It might be frozen before I put it in the eskey do you think it will defrost?