You could walk over to the Boardwalk (a short 5-10 minute walk) and watch the buskers (street performers). They usually have two out at any given point, and they rotate new ones out about every 20 minutes or so. Typically they have magicians, jugglers, clowns (not circus clowns, but more like funny mimes), etc. It is our family's favorite way to wind down the evening, especially for my daughter, who has a major crush on several of the buskers.
While on the Boardwalk, you could also rent a surrey bike and ride around the lake (it's more tiring than it sounds due to the hills and the fact that the bikes do not have different gears), hit Seashore Sweets for some candy or ice cream, etc.