Plenty of beaches to hang out and throw a frisbee, pack a picnic, paddle board, take the shuttle across the lake, grab drinks and snacks at the lakeside bar, etc. Our favorite beach is The Point, but you'll need a little cash for parking.
Stanley Lake is a bit smaller, a few miles west of the town of Stanley. A great spot to picnic or paddleboard, and there are also some trailheads nearby.
The Sawtooth mountain range is literally the land of 1000 lakes. We recommend going hiking if you have time!! Our favorite easy day-hike is Fishhook Creek, with the trailhead right at Redfish Lake. If you're interested in an overnighter, or a harder/lengthier hike, let us know and we'll shoot you some recommendations! Keep in mind, the weather in September is a little less predictable in the Sawtooths, making snow a possibility at some of the higher elevation alpine lakes.
We are not fisher-people, but if that's your thing then you'll be in a great place for it!!
FYI - you have to hike into this one!
Great spot for drinks and games, and they often have live music on Saturdays.
Another great spot for drinks and bar games!