Nice work on the cake.
What model engine is that that uses the cab as a water reservoir?
Also, is that a spare tire that you're pumping water out of?
Lastly, the guy in the back looks like he's got the catch can (like in Nascar) for any water overflow.
In all seriousness... the cake looks great. My brother in law always make crazy cakes for his kids. I give him a hard time too, but only because I can't do anything like that.
You'll have to get one of those SMF aprons if you're going to keep this up.
Points for putting the extra work in for your boy.