It's just over a mile from the resort to the Beach House. It is an easy walk, but may be farther than a 3yo can easily walk. You could get a bike with a child seat.
The resort provides a free shuttle to/from the Beach House during the day and there is good parking at the beach if you wish to drive yourself. Your resort parking pass will allow entrance to the Palmetto Dunes area where the Beach House is located.
Enjoy!