Hello, I could really use some advice. I am making a cake for my friends son who is turning 2. The theme is Mickey Mouse Choo Choo Express. I have photoshoped a cake design and want to attempt something new. I have always done my deisngs in a 50/50 fondant/gumpaste mix. I would like to try and make them out of Wilton candy melts. I feel it would be cheaper b/c I make my own fondant. I was going to just get white ones to color them myself and a bag or 2 of black. I just am not sure how much to tell my friend to buy. Here are some photos of what I want to do. It is an 18in X 12in X 2 in cake. I need to have a list in the next few days so she can get them and give me plenty of time to make all the pieces. The cake is due on May 19th.

This is the design for the top of the cake. I would be doing the balloons, Mouse ears, and maybe even the text in candy melts 

I will be wrapping a train around all four sides also make of candy melts. The train will be about 1 inch taller than the sides.

This will be the front side: 

The back side: 

The 2 short sides: 

I don’t want to have her over buy too much but I know she can return any unopened bags I don’t use.

Thank You in advance for your help.