Use href="#secondClick" to automatically scroll the page,  than simply perform a click() on the desired Element:
const EL = sel => document.querySelector(sel);
EL("#reserveButton").addEventListener('click', () => {
  // Page is already scrolled at this point since we used #hash href
  // So just perform a click...
  EL("#secondClick").click();
});
<a href="#secondClick" id="reserveButton">Reserve Now</a>
<div class="spacerDiv" style="height: 200vh;">some space... scroll down</div>
<a id='secondClick' href="https://www.google.ca" target="_blank">Click here again</a>
https://developer.mozilla.org/en-US/docs/Web/API/EventTarget/addEventListener
If you want to use a better UX (animation) you could use JS's Element.scrollIntoView()
const EL = sel => document.querySelector(sel);
const el_reserve = EL("#reserveButton");
const el_second = EL("#secondClick");
el_reserve.addEventListener('click', (evt) => {
  evt.preventDefault(); // Prevent default browser action
  el_second.scrollIntoView({behavior: "smooth"});
  el_reserve.__is_clicked = true;
});
new IntersectionObserver((entries, obs) => {
  if (el_reserve.__is_clicked && entries[0].isIntersecting) {
    el_second.click();  // Perform a click when element is in viewport
    el_reserve.__is_clicked = false; // reset
  }
}).observe(el_second);
<a href="#secondClick" id="reserveButton">Reserve Now</a>
<div class="spacerDiv" style="height: 200vh;">some space... scroll down</div>
<a id='secondClick' href="https://www.google.ca" target="_blank">Click here again</a>
jsBin live example
https://developer.mozilla.org/en-US/docs/Web/API/Element/scrollIntoView
https://developer.mozilla.org/en-US/docs/Web/API/Intersection_Observer_API