For around $2K, I think a Hobie 16 would be the best bang for your buck. It would fit an adult and three kids pretty comfortably. As they get to be adults it would be better with 2-3 people. They've been made for decades and decades, and are plentiful. I know one fellow who got an older one for $800 that had no issues (no soft spots in the hulls, no torn sails, etc.) and he's been sailing it for a few years without issue on Lake Michigan.
Hobie 16's are a blast and the speed is addictive. Grew up sailing 16's on Mission Bay in San Diego. Owned a Laser years ago, and now own a Hobie Getaway and Starboard sailboard. For a family and for fun/speed, Hobies are the way to go.
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