Shuttle transfers are required between resorts if we want to eat there. My 4 year old is not the best on long car rides. You don't need a rental car if you're staying on Disney property. We eat at different resorts and take the bus. The buses don't go directly from one resort to another, but we know how to do it from the theme parks and Downtown Disney.
Easy directions are in the book.
You only pay for the stroller once. If you change parks, just present your receipt for another. Last year was the first time we encountered mosquitos in Florida. Expect more this summer. In any event, we use OFF Skintastic in a pump spray sparingly on our children.