The playground was big and catered well for all ages. The flying fox was a favourite among the older kids, my younger one took me on a fast, loud and very imaginative drive on racing cars and we all found the rock troll forest quite cute. I believe there are plenty of events too, at least in the summer, as there was an outdoor stage and a cafe (now closed) too.
For more free or affordable family friendly tips for what to do in and around Jyväskylä e.g. this summer, you may want to take a look at