grilling question

Fathers day is coming up and my dad wants dinner to be at my place. Now I have no problem with that. I even know that it is my turn to try and convince him that he is not the only one that knows how to use the grill.
What my dad said he wants is: steak with a Chimichurri sauce, corn on the cob, potato salad (one with mayo the other without) Greek Summer Salad (just means you put in everything but the lettuce) some sort of broccoli salad and vegetable skewers. For dessert we will be having Key Lime Pie since that is his favorite. I am having one little problem though.
My dad loves Vidalia onions but I am not used to grilling onions so I need a little help. I know that my sister just adds some barbecue sauce to the top and then wraps it in foil, my aunt cores it and ads a bouillon cube and butter to the center before wrapping it in foil. Then I know others that core it add butter and salt and pepper while others cut the onion into wedges toss in olive oil and a little seasoning and grill it that way.
My dad, the guy that he is says: I don't care but he doesn't really mean that! Ugh males lol
Help... please?