We're going to see the in-laws in a month...?

And our daughter will be 2 months old. I have been pumping and storing milk since she was born (she was in the nicu and couldn't eat for 7 days) I have over 100 oz in the freezer (go me! Lol) and I plan to take some with us when we go on our trip that way if she gets hungry I don't have to sneak away to feed her I can just give her a bottle (I'm not comfortable feeding her in front on men, other than my hubby of course lol) especially since its been over a year since we've seen them. BUT its a 12hr drive. milk is only good for 24 hrs after being thawed out right? How can I possible keep it frozen for 12 hrs till we get to the hotel?