I remember this being discussed in the late 1990s. They pointed out (I think at a convention) that the difference between dying in the flood and dying at Armageddon is you may get a resurrection if you died in the flood but not if you died at Armageddon. Therefore the fact children of unbelievers died in the flood (so the reasoning went) does not tell us whether or not children of unbelievers may survive Armageddon.
Nope...died in the flood meant you were dead forever as you were executed by Jehovah directly as a judgement. Anyone executed by Jehovah never gets a second chance.