That’s going to be bad user experience for a mobile user. They will have no idea they need to tap the object to make a button appear that they then have to tap again to open the GUI.
Just open the GUI when the moving user taps on the object, and possibly have some sort of indication that the object is something clickable.
I believe mouse target changes accordingly upon the user tapping the screen but you’ll have to double check that as I tend to avoid anything that may confuse or complicate things on mobile