I'd first use the schengen lounge, allowing lots of time for passport control. Then on to the other lounge, stopping for duty free along the way, and food in not in BE. There's a beer and mussels place almost under the schengen lounge. You don't need to leave airside to shop. To kill time, on departures level before going upstairs for the nonschengen lounge, there's an art museum outpost and even a casino. I enjoy the photos upstairs of the early days of AMS and KLM. Both lounges have rather stylish showers, but there can be a wait, so be sure to sign up at the desk early if you're interested.