I had a similar experience as Donkey_Kong. My son was real interested at first, but dropped out quickly. I "made" him participate in some of the more critical parts (cutting, sanding, painting, soldering, artwork) just to expose him to these various skills. I'm glad to hear your son's got the bug.
It might be too late, but if I were doing a dinosaur theme, I think I'd go with shades of green, yellow, and brown.
For the speaker(s) you may want to consider the original Donkey_Kong, one speaker on the left side below the CP.
Regarding bringing wires from the marquee area, a common practice is to route a grove in the exposed surface, bondo over the grove with the wires in place, then sand smooth. I recently did this to bring power to a dome light on my current driving cab project.
Great progress so far.