The entire gift shop is overflowing with Magical Powder merchandise, too - from small erasers to towels with the designs, to large cans filled with snacks.
Lagunasia is about an hour east (towards Tokyo) from Nagoya Station by train and bus, and the surrounding resort also has shopping, restaurants, thalassotherapy (whatever that is), hot springs spas, a marina, and condominiums (I'm sure that includes hotel space). The park is generally open 10-5, with extended hours on busier days such as weekends and vacations. A passport that includes rides will be 4100 yen, but discounts are available for late-afternoon admission. Use of the pool adds about 1000 yen.