I like the Compacs, they make a nice trailerable boat.
However, I would warn you that many of your criteria are somewhat exclusive.
1) Must be able to have 2 adults and 4 kids on board in a pinch. It would be unusual to have everyone, but it would happen from time to time.
2) Must be able to be towed and launched by a small car.
Has to be fairly large to handle six people. But it has to be very small and light weight to be towed and launched with by a small car. Are we talking Civic small, or Camry small???
3) Must be able to be rigged and sailed single handed.
This is usually not an issue with most of the small trailerables.
4) Must have a small cuddy (for my family, this is a must).
5) Must be beachable.
Again, most cuddy cabin boats are going to be a bit bigger, and most beachable boats are on the smaller side or multihulls.
6) Must have positive flotation.
Not too unusual in a trailerable boat.
7) Should perform reasonably well under sail.
8) Should not flip easily.
9) Should not cost too much.
You want performance, stability and affordability... guess what... you can't get all three... the ones that are stable and sail well are going to be a bit more expensive, and most likely multihulls in that size range. The less expensive ones usually sacrifice either stability or performance.
10) It would be nice if it could handle heavy air.
11) It would be nice if it could double as a weekend cruiser.[/quote]
Most of the smaller boats can't really handle "heavy air" but it depends on what you mean by heavy air. You need a fairly decent size cuddy to use it as a weekend cruiser, unless you're talking about boat camping.
The small monohulls I can think of that would be good, like the Compacs, are probably not "towable and launchable by a small car." The Farrier Eagle/Tramp fits all of the above criteria, except cost. It is beachable...it has very good sailing performance... it is very stable...it is light enough to be towed by a relatively small car. It can fit six people.