E turned eight at the beginning of the month. We had a friend party for him at the Discovery Space Center which lets you go on a simulated space mission: piloting and navigating your space ship, encountering aliens, communicating with mission control, etc... It's basically like being on the bridge on Star Trek. The kids really loved it.
Our house is on the smaller side and I wasn't thrilled about having a pack of 8-year-old boys bouncing around it so the cost seemed very reasonable, especially since I used a $50-off coupon I received on their mailing list.