HeadIndex Mod Kicked Off with a Button

Hello! 
I am working to get the HeadIndex mod to be kicked off by a button push. I have that working but I have 2 questions/problems.

I have a called function that executes this command: 
execute as @p run head

Where is the @p centered? Is that the correct (or most correct) target for the function? The center for the function does not appear to be the button. For example I am standing in front of the button and I press it. A person behind me gets the menu. 

How do I have a function call only run once? Since I have the call on the tick, it opens the menu multiple times.

Here is the code I am working with.

tick.mcfunction
  execute if block 382 68 -2473 minecraft:oak_button[powered=true] run function headindex:headmenu

headmenu.mcfunction
  execute as @p run head

load.json
  {
    "replace": false,
    "values": [
        "headindex:load"
    ]
}

tick.json
 {
    "replace": false,
    "values": [
        "headindex:tick"
    ]
}