Not the parent.

People want to do stuff, and they want to get it done fast and in a pretty straightforward manner. They don’t want to follow complicated steps (especially with conditional) and they don’t want to relearn how to do it (because the vendor changes the interface).

So the only thing they want is a very simple interface (best if it’s a single button or a knob), and then for the expected result to happen. Whatever exists in the middle doesn’t matter as long as the job is done.

So an interface to the above may be a form with the start and end date, a location, and a plan button. Then all the activities are show where the user selects the one he wants and clicks a final Buy button. Then a confirmation message is displayed.

Anything other than that or that obscure what is happening (ads, network error, agents malfunctioning,…) is an hindrance and falls under the general “this product does not work”.