Moving across country with frozen milk

Dandalf03

We are moving in a few weeks from NV to WI.  Flight is about 4 hours, plus 2 hours in the airport.  I have A LOT of frozen milk (maybe 200 oz). My FIL is here right now and I was thinking of sending half with him, but I am not sure if they will let him fly with it without LO.  I am also not sure if it will make the trip frozen.  I also read about shipping it. Does anyone have experience with this?  Any other ideas?  I thought maybe if we check it when we fly it would stay frozen, but not sure if checking it is the best idea either...