Most of the tours involve water activities, especially snorkeling and diving. Shoretrips.com has an 'ultimate island tour' of 6 hours which includes stops at the ostrich farm, liquor distillery, and dolphins.
I haven't been to Curacao in ages so I don't know what is currently 'hot' as a tour.
Saw the 10 spaces requirement too and thought it odd. I haven't been to Curacao in ages. That last time I was there I went to the Sea Aquarium. It was really nice. I just took a taxi there. Back then, they brewed Amstel Beer on the island. On Curacao it was called Amstel "Bright" instead of "Light". A very tasty beer I recall. I think they have their own Sea Water Desalination plant there, or used to. I recall a lot of the ship's crew bringing water back on board.