I would go with Beach Club or Beach Club Villas. Storm-A-Long Bay would be great for the ages of both children. You have a zero entry sand bottom pool, lazy river, waterfalls, slide, etc. Plus, you have the convenience of being able to walk to Epcot and take a boat or walk to MGM. Its just a change of pace from relying on the buses all the time. In addition, you are in close proximity to the boardwalk to walk or boat over to there.