The president does have broad power as the head of the executive branch to conduct its affairs: look at the history of the creation of the Department of Health, Education, and Welfare under President Eisenhower's Reorganization Plan No. 1 of 1953. Congress was only involved when President Eisenhower asked for approval for the reorganization of the Federal Security Agency into a cabinet level Department.
But beyond that, I read NSPD51 and it didn't strike me as anything odd. The language is very similar to most continuity of operations planning that you see, and I didn't see anything that took it beyond the bounds of the executive branch of government.
Maybe I am not seeing some point that is troubling, but to me seeing the administration simply doing contingency planning limited to the executive branch isn't of itself that worrisome.
Same here. Lots of knee jerk reactions from people looking for hidden meanings, hidden messages and evil government plotting.
Somtimes a cigar is just a cigar.
(Or it used to be until Bill Clinton stained the image)