Here are two wooden trucks I made as holiday gifts for our nephews. The cabs were made from mixed offcuts (and I'm a little worried I failed to consider different expansion rates for different species), the trailers from hardwood ply. The paint was non-toxic acrylic with a non-toxic gloss coating from an art supply store. Getting the axle holes aligned so that all 18 wheels turned was a real challenge and I didn't succeed entirely.
Fun project, but I couldn't believe how long it took me. But, as you can surmise from the last photo, they went over pretty big.