I'll second that. Some of our nest beach vacations have been taking the boat up to Lake Huron or driving across to the sand dunes on Lake Michigan.
We did the Mayan Riviera once and didn't have issues with mildew or bathrooms or anything. We stayed at one of Wyndham's all inclusives, but next time we're going to step a little further out of the comfort zone and stay at the Occidental Xcaret for the proximity to the eco-park.
Another beach that we've really enjoyed through the years is Virginia Beach. The location is great because you've got a long stretch of public beach on the Atlantic and a state park with a beach on the Chesapeake if the surf on the Altantic is too strong. The marine science museum there is really cool - my kids love the sting-ray touch-tank in particular - and there is always . And there are some other neat attractions nearby enough to make good daytrips or diversions on the drive to/from home. We've visited Kitty Hawk, gone to see the wild ponies on Assateague, took the scenic route through the Blue Ridge Mountains on the way home so we could tour caverns, stopped at a couple Civil War battlefields, even spent a couple days in DC to hit the Air & Space Museum on the way down once. It isn't a great destination if you are looking for some place where you can fly in and not drive at all, though.