Breastmilk Storage

My husband and I live on the east coast, but two of our friends are getting married in Chicago next weekend (the 15th). DS and I flew out last weekend to visit my parents in Iowa, and then my parents, DS and I will be driving to Chicago for the weekend of the wedding, and DH will be meeting us there. My parents are going to watch Wesley (DS) from Saturday morning through Saturday night (if I can manage to be away from him for that long   ).
I am pumping so that they will have enough breastmilk to give him while we are away, and storing it in the freezer to ensure that it will stay fresh . During the drive, we will be transporting the milk in a cooler that plugs into the car (so there's no worry about the temp getting too warm). Now I know that once frozen BM is thawed, that it has to be used within 24 hours. I'm wondering, though, is that from when I take it out of the freezer to when he drinks it, or from when it completely thaws until he drinks it?
The BM will be put into the cooler Friday afternoon (around 5-ish). Will it still be good until about 8-9am Sunday morning?

According to kellymom.com it's 24 hours after it has completely thawed.