Nope, don't think you're overreacting at all. I agree that if they are worried about the milk not keeping why can't they give it to some of the other kids as well? I keep UHT milk at home in case I run out of normal cows milk and have given it to DS a couple of times and he's been none the wiser.

How much milk does he have in a go? When you say you could supply the 200ml pack - why can't they just buy some of these instead of the big ones?

If it were me I would supply the little ones for a few days but say tht you expect them to get their "stuff" sorted asap. It's really not like what you are expecting is a lot...

Good luck!