Thanks all!

I'm thinking I might keep it refrigerated and then take it home with a few ice bricks so I can freeze it when I get home.

Taurean - I have that cooler bag and ice brick you are talking about but not sure if it would be big enough for 3 days worth of milk (1.2-1.5L possibly?!?).

Am going to do a trial run with bags of water and see how cold they are kept for 8hours. Will keep you posted!!