Glad to hear that you're coming to Curacao. Divers definitely want to stay in Banda Bou; the west end of the island. The diving is much better than near town.
There are a lot of places to stay that cater to divers; Habitat, Sunset Waters, All West Apartments to name a couple. There is a high end hotel; The Lodge Kura Hulanda. You could also stay 1/2 the week at the Kura Hulanda in town and get the shopping part of your vacation over and then 1/2 at the Lodge out in the country. You can look at Vacation Rentals By Owner (VRBO) or Home Away and rent a house or apartment. There are budget apartments like Lagun Blou or All West. We have a 3 bedroom vacation apartment in Westpunt if you'd like more info, let me know.
In our opinion and since this is "scuba" board others will agree that most of the dives can easily be done by shore. Our local dive shop back in NH wanted us to put together a dive package but I couldn't justify an $80 2 tank boat dive or even $30 a day for unlimited air unless you plan on 4 dives a day. On the west end you can get air at Habitat, Daibooi, Porto Marie, Cas Abou, Sunset Waters, maybe Santa Cruz (?), Lagun and Kalki for just 6 to 8 dollars a tank. If your wife and daughters do not dive, the snorkeling is great at Lagun, Cas Abou and Porto Marie. There are also small reastaurants there so you could have lunch with them during your surface interval.
A lot of divers stay in Westpunt. We've met quite a few at our weekend restaurant and been dive buddies during the week.
Most only go to Willemstad once during their stay; usually on the day before they fly home, preferring to dive everyday. The drive downtown is only 40 minutes.
The other side of the coin would be if you stayed at Breezes or Lions Dive, you might end up only diving the east end spots; which there are quite a few nice ones including the wreck of the Superior Producer and not bothering to drive "out west". Depending on the ages of your teenagers, they might want to be at Breezes, Lions Dive or the Royal Sea Aquarium so they can walk to Mambo Beach or Wet and Wild to the party scene at night. There is no party scene in Banda Bou and I think the entertainment at Sunset Waters etc. might be a bit tame for kids.
Curacao has something for everyone, especially divers. We moved here last March and have become a part of our area and even around town. I don't think that the locals are unfriendly at all. Many are a bit reserved but all will gladly help you with directions and such and will certainly talk to you if you initiate a conversation. There is petty crime everywhere. Leave your skis unattended in the NE and you risk not skiing in the afternoon, pockets are picked in every major city. It's the same everywhere. Please get insurance on your car. Chances are if you are to run into any problem it will be someone breaking into your car. Do not leave anything inside. In 11 months I have only been asked for money once. There are kids/people at the grocery stores, the dump, and some gas stations that will help you for a guilder (.57) or two but in my opinion they are attempting to work for it. Your friend may only be used to US customs and standards. The lodgings here are only 2 or 3 star facilities and should be accepted as such or as I suggested, rent a place on your own; many do.
Hope you have a great trip. Let us know if you'd like company on a dive. We live a third of a mile from Alice in Wonderland; it's our favorite dive site.
Sunshine
Curacao Sunshine - Rental Property on the Island of Curacao