My kids loved WS as well. They were 5, 5 and 8 and they did the Agent P game over by Japan (one of the three I believe) and had a blast...it was so hot we were melted by the time we got finished chasing them around between the points they were sent to. They've already decided they want to do the other two portions this go around next May-June. They stopped a couple of kidcots where the 5 year olds colored...8 year old not so much.
We hadn't planned a whole lot of time at WS but are planning an entire day for Epcot this go around, if not more (but are also staying 8 nights). I'd say go and let them see it. If its not for them, head back over to MK (if you have Park Hopper that is)
Another thing my kids love....looking through all the countries gift shops!