Fun, reliable, 4 seat convertible

There are several directions you could go with this. The Germans's make several solid options, VW Eos or Bug are fun options. Then there are of course the BMW/Audi/Mercedes midsized convertibles which you can probably find used in your price range. These might all be higher costs to maintain, but at only driving a few thousand miles per year, they will be plenty reliable.

You might look a little outside the box. The Jeep Wranger is actually a really fun convertible and they hold their value extremely well. Nissan also made a strange but interesting Murano CrossCabriolet convertible. They didn't sell well, so you can get them lightly used for very cheap if you can find them. There is also the old standby Mustang convertible.

You probably know whether or not the Ford Mustang appeals to you. People who like Mustangs tend to love the current one. Unknown: whether a 2015 can be purchased with the features you want for $30,000. The previous generation doesn't drive nearly as well.

Among upscale four-seat convertibles, the Infiniti Q60 (G37 before 2014) is probably the best value. New ones might be heavily discounted.

For a little more money than the Infiniti, the Audi A5 and S5 are at least as beautiful and are more refined, but are also more expensive to purchase and to maintain after the warranty ends.

A convertible that seat 4 under $30,000 would be the brand new Buick Cascada. It retails for right around $30K but is discounted almost 1/3rd to $20,000 advertised on the Internet for sale websites.