What i have seen is that when a menu is shown on iOS devices, you had to click menu items twice. like first click is to choose and second is to go.. not sure how else to explain it
So, you press the Parent link first and it expands the children links, then when you press the Parent link again the children don't minimise but a new action is introduced and the Parent link goes to another page?
You can introduce what ever functionality you want, and we can recommend the JavaScript to help you, but choosing what the theme should and should not do is a usability question that should first be explored in user testing.