It's Willemstad. Google Earth puts it at 5.2 mi. to the Punda side - all the colored shops you see in the ads. The open air market is there, the floating fish market etc. The old synagogue if that's of interest - oldest in the Western Hemisphere. Museum Kura Hulanda also - never been there.
From there you walk across the famous swinging bridge to the Otrabanda side where there's the Rif Fort complex - shops, restaurants etc. Also other shops/bars since the cruise ships moor at the Mega Pier there. - some along Otrabanda downtown also. The Renaissance there has the nicest casino on the island - like one in Reno.
A mile or two farther west and you're in Piscadera Bay - another resort area. The Marrriot is a nice complex with plenty to do - watertoys, nice beach etc. Small casino, a couple of bars etc. They have a very nice pool bar complex. I mention it because they have a nice protected beach and you can buy a day pass. At one time they had those ride-on Snuba things in the bay there also - the ones where your head doesn't get wet. Pirate Bay is a funky little beach bar there that should have music some nights. PBay is a little quieter at night.
How does your friend like beaches? Many of them are also dive sites so with a little planning you could meet a guide and dive then hang out. Varsenbaai is good for this - snorkeling with turtles, decent beach, restaurant and Trunk Divers all on-site - Playa Lagun also except the best bar is at the condos to the north. great view and open to the public.
Bas Harts Diving does escorted shore dives. Or if your friend snorkels you could both go with the Dive Bus. They'll pick you up or it's only about 2 mins. from your resort also.
The aquarium area itself is a tourist stop so besides the facility there's a few shops/restaurants and nearby/resorts. Nice beach bar at Lions Dive resort - across the channel from RSA - you can easily walk to it. Next to it is the Kon Tiki Resort. There's more than a dozen casinos also - most are downtown. And several jazz clubs. Mambo Beach is one of the popular beach clubs - it's about 1/2 mile west +/-. Avila Hotel has a Jazz bar some nights it's live.
Going the other way, the Jan Thiel Beach area is pretty popular with tourists. You can dive there - set it up with the shop on-site if you need a buddy. You have to drive north then east around Jan Thiel Bay to get there though. The Ostrich Farm is north from Jan Thiel about 5 miles - close to the north shore. It's cut-off on the image below but it's labeled the Curacao O. The Aloe Vera farm is there and something else. None are close enough to walk between afaik so best when you have a car.
If your friend golfs, Santa Barbara Resort is the next bay over from Jan Thiel.
There's a tourist trolley train that runs around on the streets downtown - IDK any details, just saw it once. Really just about everything in Curacao unless it's nature based is in/near town. I understand from a friend who used to live there that the buses are pretty reliable also.
fyi, even though Willemstad is marked with a star on this image, the heart of the shopping/tourist area is near Otrabanda/Punda.
