First of all, we need to thank Ronald Reagan for even having this option.
Second, the worst thing would be to do nothing. North Korea is well aware of the success rate of our ability to shoot down missiles and will not be encouraged or discouraged from our success or failure. The key is to demonstrate that we are willing to use the technology and to learn from its use. The United States HAS to let it be known that, since North Korea has announced its intentions to target a population, any launch from this point further will be considered an act of war. Trump MUST make this clear.
Third, if we wish to protect our intelligence on anti-missile missile technology, we would need to take out North Korean tracking abilities between the time of launch and the intercept attempt. Also, each missile that we intend to intercept must also be accompanied by a strike on its launch site...which we have a great success rate for.