pumping

I'm Gona be leaving my son with his father for three hours tomorrow. I'll feed him before I go but will also pump in the morning just incase. I'm not sure if my son will need the milk while I'm gone. What's the best way to store it? Leave it at room temp and freeze it if he doesn't take it? I don't pump enough to leave at room temp. And if I leave it in fridge he'll have to warm it up so I won't be able to freeze it.