Have you checked out Treasure Island? My Mom loves Treasure Island, and she's a very "active senior." Treasure Island Beach has a beach side sidewalk (behind the hotels and restaurants) that locals call the prominade; it's a wonderful way to get some exercise, take in the sunset, listen to the beach bands, and "commute" to all of the restaurants, nightclubs, grocery stores, drum circles, fireworks displays, and other beach events. Treasure Island has a nice central location (it's main attachment to the "main land" is, in fact "Central Avenue" which is the main West-East road from the Beach to downtown St. Petersburg). When we lived in Isle of Palms on Treasure Island, we walked or bicycled to virtually everywhere we needed to go (walk to beach, bike to John's Pass; bike to health food store, Mall, Beall's Outlet; walk to grocery store, book store, etc.). Mom uses a small local golf course in Treasure Island, but there are several other golf courses within a short drive, and there are numerous tennis courts, ball courts, ball fields, etc. within a 5 to 10 mile radius. Mom lives in a "walk up," but some seniors prefer elevator or ground floor locations in view of ease of grocery bag "hauling" and potential future mobility considerations. Not sure if it would be right for your parents (as it's a second floor walk up), but here's a link to a nice 2/2 Waterfront Condo with panoramic waterfront views, deep water boat slip, and 2 parking places, located only 2 blocks (about a 5 minute walk) from Treasure Island's public beach and boardwalk: http://www.trulia.com/rental/3072793381-11045-3rd-St-E-Treas
You can also get to the virtual tour from http://www.youtube.com/user/TreasureIslandCondo
It's available for rental at $1450/month; but owners are open to future sale with seller financing available. Good luck with your search, and welcome to the beautiful Pinellas County Florida Gulf Coast!