Custom Train Faces

This is a Birthday present for my Nephew's 4th birthday this week.
I've been working on this on and off when I haven't had other projects for a few months, but never ended up with more than a blob of plastic. I finally realized today that the small base might be the root cause of the problem. I merged the model with flat cylinder and it worked moderately well.
Check it out:
http://www.thingiverse.com/thing:62964
printedsolid.com