Hi there,
We'll be in Kiel for a day in mid June on a Baltic cruise. We have a family group of 3 grandparents, 2 parents and 2 six year olds. We like to hike, do self-guided walks, visit museums, and take tours of public buildings (ie City Hall, local seat of government, etc). The kids love to play outside, eat ice cream and visit fountains too.

We're happy to just explore and do low-cost things.
Any suggestions?

To be frank, Kiel is not the most fascinating city. Here a few tips.

- Schleswig-Holsteinisches Freilichtmuseum is an open-air museum of around 60 farmhouses. Within the city.

- In Schleswig, there is a Viking museum/archeological museum with a full-size (original) Viking ship and bog bodies (mummies). http://www.haithabu.de
You take the regional train from Kiel to Schleswig (50 min) and from the train station the bus to Haddeby stop. The Viking Museum Haithabu (that is the name of the Viking village) is on the original site, NOT on the site of the archeological museum to which it belongs.

The open-air museum is in the suburb of Molfsee and can be reached by bus from the train station. Yes this is worth seeing.

Weather permitting, take the Fördedampfer (boats that run on regular lines like buses all over the harbour) to Laboe. Climb the marine monument for the view, go for a walk along the beach (it may or may not be warm enough for swimming) and see the museum submarine.

When I was little (my Grandma lived in Kiel and we visited often) I loved watching the big ships in the canal locks at Holtenau.

an update: We ended up just touring around Kiel itself and had a lovely time! The weather was sunny and warm, and we hit some parks as well as an outdoor international cultural festival. Highlights were playing in a high tech water fountain, riding pedal boats on the lake, and seeing the Tall Ships sail out behind us as we left the port. (We lucked out with a table near the window - fabulous views at dinner!)