Posting of the 10 Commandments poses no problem. No coercion, no punishment. The pledge is more borderline. There should not be any requirement to participlate. It needs to be voluntary or 'under God' should be removed.
Can the Vice-President or the Secretary of State issue religious recommendations? What about the Assistant Secretary of State?
What happens if the President recommends speaking in tongues but the Governor of Texas advises against it?