An “official act” cannot be simply anything a President does. It should be either enumerated directly in the Constitution (like the pardon power, or the right to make cabinet and judicial appointments), or an authority given to the Executive through legislation.
There is no role for the President in the electoral process at all. The Constitution offers him no role at all. He is not responsible for ensuring elections are fair, the elections officials in the different states are. I see no possible way that provisioning alternate electors, which were not the ones that were ratified by the States, could possibly be within his official duties.