"Oh, poor children!"
Translation:¡Ay, pobres niños!
Often, pobre after the noun means without money; before, it means deserving of pity.
But there's no context given. This person could just as well be talking about children without money. "Niños pobres" should still be accepted.
I think pobre (poor) is not a verb and does get conjugated as pobro, pobras, pobre. Pobre is an adjetive and so is pobre (singular) or pobres (plural).
I don't see that anyone has yet reported that "niños pobres" should be accepted, and I don't see any compelling arguments for why it shouldn't be accepted. So I just reported it!