I'm absolutely confused as to what you want because you seem to know what words should or can be interposed into those sentences from what you've written above:
We explained our situation to the security standing at the entrance. However, I think there is little chance they will ...... what we said to their supervisors.
(they will convey; they will relay; they will relate)
If you were to reword the sentence, these verbs could be used:
...I think there is little chance they will ...... their supervisors (of/with) what we said. (If I put "with" in parentheses below, it does not take "of" after "supervisors"; it would most likely take "with" then.)
(they will inform; the will acquaint (with); they will
The decision taken in the meeting will be ..... other employees (through/via/by) email(s).
(will be conveyed to; will be transferred to; will be
transmitted to; will be relayed to; will be related to; will be sent to)
The preposition "via" sounds better here, but this may just a stylistic choice, although I think most native speakers would use "via" or "by" in this situation. I also think that "email" should be singular unless the company should be trying to convey that more than one email will be sent to all of the employees regarding the decision taken in the meeting.
I hope this might have helped you out. Take care and good luck!