Badger Sports Park in Appleton bills itself as an entertainment center. They have a pretty good selection of activities to choose from. It looks like the older your family is, the more they will be able to participate. A few of the attractions have age restrictions (laser tag, go karts), others are just not realistic for the littles (batting cages).
This place looks like a lot of fun for an active family. It could definitely add up, though. There are hourly or daily passes (with some exclusions); you can also pay a la carte per activity.
Badger Sports Park
3600 E Evergreen Drive ~ Appleton, WI ~ (920) 830-6900