Keftzova (aka Kiftzova) is an indoor/outdoor play space for kids - probably best for the under-10 set.  It has many large inflatable slides and jumping surfaces, as well as a few small rides (train, mini-motorcycles).  Indoors, there are some game rooms, a lego room, a "mini-gym," large and small ball pits, computer stations, and other forms of entertainment.  There are picnic tables in the outdoor space - which, as a big plus, is fully covered so you're not out in the blazing sun. 

 The park is located about 20 minutes outside of Jerusalem, on a mountaintop with gorgeous views in every direction.  Admission is about the equivalent of $9/adult and $11/kid.  If you're going with a lot of kids, or planning to go more than once, there are discounted 10-paks.