I found a few cake pans on Amazon ad showed them to Liam. He took a look at the dump truck cake and then the tractor cake, and gave me a very emphatic No.
So then we googled construction-themed birthday cakes and found something more agreeable.
Something like this:
Molly and I stayed up late with my mom the night before the party to finish the cake. We had a lot of laughs over the "dirt pile" behind the trucks on top.
After singing Happy Birthday and Liam spit/blew out all three candles, each of the kids took a truck to lick clean. (The trucks are from a Melissa and Doug puzzle purchased new for his cake...).
After licking the trucks clean, they moved on to the cake: 1, 2, 3, 4 Cake from Alice Water's Art of Simple Food with Chocolate Sour Cream Frosting from Martha Stewart's Cupcakes. Yum!