The race does finish in the parking lot but the runners get to go through Epcot just before finishing. To see them at the actual finish line is very difficult because it is crowded. I have run 2 Disney halfs and my recommendation would be to go into the Epcot and get as close to the walkway that connects Future World and WS as possible. As you are finishing you run down one side of the walkway and back up the other so you can see him twice.
This of course depends on how quickly your husband is running the half. FW opens at 9:00am that day. You will have to look at his coral and pace and determine if he will get through Epcot too early. Another good option is to wait over at the bus area to watch him enter Epcot. You can then head over to the finish area and by the time he runs through Epcot, the finish queue, and gets his goodies you can see him over at the package pickup.
Im not trying to discourage you from watching him finish but I dont want you to get to the finish area and not be able to get a spot to see him finish and then miss him all together.