I love this. One bit of advice I'd have on the layout is - I think the area with all the zombies and the displacement floors is an area where water would flow ? but it doesn't seem to have an obvious outlet near where you enter. (44 seconds)
I too am married with kids attempting to devote more time to mapping and modeling for hl2 since I had a very long break.
This is a great thread and project, I love to see prototyping videos.