Wow, what a task to set yourself, great cake idea! I have a recipe but you need to see the pictures, and I’m unsure how to upload them to this comment. I can do one but there’s more then one. Hope you found one

Good answers, how did you go with the cake?

Honestly the cheats version would be the easiest and a three year old won’t know the difference. By that I means just get a round cake and one of those edible pictures. You can even get them personalised to have your sons name on it.

i think that you should google it! then you can see the finished results and it will be easier to decide

If you can get your hands on a woman’s day cake cookbook they have the best!

Maybe you’d like to check out this page! It could give you some ideas!
http://tipsfromamomof3.blogspot.com.au/2010/02/dinosaur-train-birthday-party-frugal.html

For a Dinosaur Train Volcano Cake Idea – Lay a Bundt cake on top of a 9″ square cake. Completely cover the cake with chocolate frosting. Make orange frosting by adding 5 drops of red and 3 drops of yellow food colouring to white frosting. Slowly pour the orange frosting around the top to resemble lava flowing out of a volcano. Write a happy birthday message with white icing on the front of the volcano. Arrange plastic dinosaurs and trees around the bottom of the cake and place a small train around the outside of the volcano.

thankyou for your advice, i will post a picture with my finished product

No sorry i dont but i have found a web site called how to cook that, i recently made a cinderella cake off that site. My daughter loved it and was a bit hit for her party. They have many different cakes etc to choose from. The best bit is they have a recipe for cakes etc and a tutorial that talks you through how to make and decorate it.

I made an ordinary cake, used a cupcake to make a boulder, and stuck some plastic greenery and mini Dinosaur Train figurines on top. It wasn’t spectacular, but my son loved it.