“Cynical” – “conservative” conversions are NOT k’halacha. First of all, most “conservative” “rabbis” (let alone laymen) do not even accept the 13 ikarim, do not accept Torah mi’Sinai. That goes double for Torah she’baal peh. The Torah, they will tell you, was written by a bunch of “very wise men”.
Having THAT as a starting point… it goes down hill from there. Do you really think that any woman undergoing a “conservative conversion” accepts upon herself observance of mitzvos -observance of Shabbas, kashrus, taharas hamishpacha??? Most definitely not. Even the “rabbis” who convert them are not makpid about these things themselves.
So, to answer the original question… Of course if they are Jewish through maternal lineage, then of course they are Jewish. But if they are Jewish through a “conservative” (or “reform”) “conversion” -or the child of a mother from such a “conversion” – then clearly they are NOT Jewish.