Do I really need a dedicated park board, or can I just use my all-mountain board in the park?

You can absolutely ride an all-mountain board in the park, and many riders do. However, a dedicated park board will make learning tricks significantly easier due to its softer flex, more forgiving profile, and lighter swing weight. If you ride park 2–3+ days per week, a dedicated park board is worth the investment. If you only occasionally hit the park, your all-mountain board is fine—just be more cautious on rails since stiffer boards with camber profiles are less forgiving.