If you get a cab and ask the driver about the beach, he will know exactly where to take you where you can get food, lounge chairs, etc. There are also areas of the beach where you can rent jet ski's, etc.
We just got back and hopped into a cab and was dropped off at the beginning of 7 mile beach there was a little restaurant there with restrooms. There was chairs on the beach. We only had about 2 hours there. I had conch fritters and my daughter had a cheese burger. Food was good. Beach was quiet and not a lot of people and you could walk the 7 miles if you wanted. Just tell cab driver what time you want to be picked up or walk out to the end of the driveway and hail the 1st cab you see going in either direction.