I would like to do a hotel points run with my family to Karlsruhe this summer. Are there things to do in the area of Karlsruhe for a weekend getaway?
Heidelberg is close by...

Baden - Baden is also not that far away (train connetcions) and offers some nice sights and museums (e.g. Burda Collection) as well.

A visit to "Karlruhe Schloss" and stroll through the city (called "F�cherstadt") would be programm for a day.

Make sure you visit the ZKM - a must see when you are in town:
http://on1.zkm.de/zkm/e/

take a day to travel to Baden-Baden. nice town to walk around and dine (though not that cheap though). there are lots of concerts in summer. wonderful thermal bathing.

in Karlsruhe - schlosspark is a good place to relax. museums (including the one ft_nick mentioned above)are also worth visiting

Allow me to link a couple of travel pages I wrote over on Virtualtourist.

First, a *few* tips about my dear hometown: http://members.virtualtourist.com/m/f86bd/bdf4/
In case you are here on the first weekend in August, there is the Long Night of the Museums on Aug 4.

Baden-Baden: http://members.virtualtourist.com/m/f86bd/12d15/
Rastatt: http://members.virtualtourist.com/m/f86bd/67cd/
Ettlingen, Karlsruhe's next-door neighbour: http://members.virtualtourist.com/m/f86bd/fcb4/
A quick hop across the French border to Wissembourg: http://members.virtualtourist.com/m/f86bd/13f89/
The vineyards of Palatine, for example around Edenkoben: http://members.virtualtourist.com/m/f86bd/105ee/
A hidden gem if you like small old towns is Eppingen: http://members.virtualtourist.com/m/f86bd/ff41/
Park and palace in Schwetzingen: http://members.virtualtourist.com/m/f86bd/4bcc/

Then there are endless options for hiking in the Northern Black Forest, the Palatinate Forest and the Kraichgau hills.
The Cistercian abbey of Maulbronn UNESCO World Heritage.
Cities like Strasbourg, Freiburg, Speyer, Heidelberg, Stuttgart can be reached in an hour by train.

... just to name a few options. We could easily keep you busy for several weeks here!

First thing to be aware:
Karlsruhe is getting a subway downtown. They put the downtown underground so downtown is quite a construction site.

To all the ideas above I would add:
Take the tram to Bad Herrenalb and take a short hike through the Black Forest.
Depending how old your kids are maybe the zoo in Karlsruhe might interest them.

I also went to Karlsruhe this summer, for a week. Must say, Karlsruhe was pretty awesome. The neat thing about Karlsruhe was that it was pretty close to other cities as well, we also checked out Strasbourg. Hope you checked out Heidelberg!!