Awesome. Though, ya know, I think I'd not build this with stairs, I'd build it with an enclosed slide that seals shut with a metal door at the bottom. This way once your whole family gets down there, you can seal it up just in case your hideout is found.
Make the most of your under-stairs area with this stylish and practical idea. Create a secret hideaway with a pull out drawer, like this one from Smart Storage, perfect for a family home. Find more ideas at housebeautiful.co.uk