As far as I know, Trump has no way of deciding on the national reserve issue himself, the president does not have much power when it comes to national reserves. Any bill relating to national reserves must be considered by Congress, no one has authority in this matter, not even the president.
I know everyone is excited about the bitcoin reserve plan but we should know that Trump cannot decide on that and it will take a lot of time.
Congress is controlled by republicans with a slim majority, but even then it would be hard to pass the bill because not all the republicans agree that a strategic bitcoin reserve is a good idea.
Trump's main goal is to make the United States the center of cryptocurrencies and become a leader in this field, he is interested in the crypto industry, not just bitcoin. I even believe he would probably pay more attention to altcoins than bitcoin, he is not a bitcoin maximalist.
Elon in particular would try to make the government do transactions in Dogecoin (that coin that doesn't even get any active development), if only for the memes.