If you can play fine with Pets and Seasons, the other EPs shouldn't be too much of a burden, since those two are usually the breaking point for lower-end computers. I played with every EP except for Island Paradise on a laptop far worse than yours, and while performance wasn't perfect, I was able to play on it without much frustration.
Now, too many EPs can slow your computer down, but I think you'll be able to handle Supernatural just fine.