Yes, if you intend on running said action that depends on or fetches data from the array as soon as possible after loading the array JSON data into memory.
Practically though, no user should be able to click on something or do an action faster than your device can load the array on start of layout.
If you want to be really proper about it, start with your buttons or user interface disabled, and add an action to enable them in that same event with on ajax finished and array loaded. This guarantees the user can't do anything until at least the array is ready. For automated tasks and functions, yes they should be called in that event as well, so they run whenver the data is available.
Separate event sheets or includes has nothing to do with anything, you can do that or not, up to you.
Edit: Event sheets don't store arrays...? You're definitely misunderstanding something.