We found two great places to take kids for a fun day out. They both have low admission charges and are beautiful parks with lots of play areas, swimming pools, kids museum, animals etc.  There’s lots of different things for the kids to wear themselves out on while the parents picnic on the grass. Bring a change of clothes and a towel for the water play areas.

http://www.maximilianpark.de/  (50 mins from Bielefeld)

http://www.vier-jahreszeiten-park.de/ (30 mins from Bielefeld)