I built a loft bed for my husband and I, actually. I LOVED having a nice cozy little place to sleep :) It isn't terribly hard to do, it's just a matter of building the framework and then having fun with the external design! I should hunt down some photos and make some posts about it.
Coloring books would be GREAT! You could even do a "Mommy and Me" type coloring book with the prevalence of so many "adult" coloring books! They could be in pairs and you could offer free printables to get people to participate and get the word out :)
I'd love to see posts about your bed building! I've built a book shelf before...This would just be like a very large shelf, right? ;-)
parent-child coloring would be awesome!