I would only emphasize that mid-September is a time when you want to make double-sure your gear (and you) are ready for whatever weather you may get. For example, it's no time for a tent that's past its prime or has never been tested in strong winds or downpours (personal experience). An extra fly and some extra warm clothes like fleece jackets/stocking caps in a dry bag may prove well worth the extra weight. Finally I'd suggest you take along some lightweight long-johns. (I like "Wickers.")  --Goose