How to make a menu controled from Keyboard and using buttons?

Hello! I'm working on a Turn Based Game like Final Fantasy Tactics, Disgaea or Xcom, and right now i'm trying to do the "actions menu". The game it's meant to be played with a controler using the arrows/joystick to move around the grid and the menus. These are my problems right now:

1. I need to highlight the pre-selected button, so the player knows what button it's going to be activated when he hits "Space" in the keyboard

2. I don't know how to activate my selected (and highlighted) buttons through the keyboard (the OnClick() function works when i click it with the mouse.. and i'm not playing with the mouse); How can i do this?.

this is the hyerarchy of my canvas: http://gyazo.com/715083dbe07f8a93ba72e16023ace6b5

And to manage the UI, I'm using a Script called Hudmanager that it's in charge of all the changes applied to the buttons, the panel and all the UI elements.

Thanks for all the help!