You want the lanai to be at least 12 feet wide. (Think a 5 - 6 foot round table with people sitting all around it).
Also make the garage as large as possible, deep and wide. Most cars are about 16 feet long so an 18 foot deep garage gives you no room front or back. Also make the cart garage deep enough for 2 carts. A standard cart approximates 4' X 8'. Even if you don't get 2 carts you will fill in the extra space with "stuff". Remember, no basements in TV!
Another tip, put in an extra wide garage door, I believe it is 18'. Well worth it.