First, to delay assembly, you tell the toddler that it would be nice to save the train for when grandma and grandpa arrive in three weeks (like the toddler would agree to that idea even if the grandparents were due to arrive in three hours). What if we wait until Daddy comes home? No.
Because you don't have the right sugar to make the frosting, you mention the idea of going to the grocery store to buy the icing sugar. Of course not. So you make do with regular sugar. While you make the gluey frosting, the toddler proceeds to unpack the gingerbread pieces from the box and nibble on most of them. Fine (although you wonder about the ingredients now entering the toddler's body as they came from an item that is packaged loosely in a cardboard box, without any airtight plastic). You are flexible. It'll be cute to have a train that has his unique little teeth marks in it.
You try to follow the pictorial instructions, separating out the different shapes to make the engine from the ones to make the coal car. Since the toddler continues to eat the gingerbread pieces, you don't have the time to distinguish the miniscule difference in size between the rectangles so you just start building. You realize early on that you really need to hold the pieces in place while the icing hardens (this is either by design or you didn't make the icing thick enough). You ask the toddler to hold a piece in place. No. He pulls off the piece and takes another bite. You'll need to do the building yourself.
Meanwhile the toddler has lost interest and begins to play with other things on the table.
You finish the engine and ask the toddler to look at what you've constructed, hoping to verify that what you built actually resembles a train. The toddler says, "train." You are happy.
You move onto the coal car. You realize that the engine didn't quite fit on its base b/c you used the wrong gingerbread piece for the base. You will have a train with a small engine and a big coal car. Then, as you build the coal car, you find that it isn't squared properly b/c you used the wrong pieces when building the sides of the engine. Nothing additional frosting can't fix.
You decide to engage the toddler in the process again by having him "glue" some of the decorative candies to the train. In hindsight, you KNOW that a toddler does not have the gentle touch to decorate the train without collapsing the sides so you quickly decorate with the candies yourself (seem to be missing the blue candies).
Finished. You look at the picture on the cover of the box then look at your train. You realize that the instructions asked you to make a tube to squeeze out the frosting for gluing and decorating. While the glops of icing from using your fingers are functional, the train is admittedly not very pretty. There is no way to decorated the train with icing using your fingers. Fine.
An hour later, toddler climbs on a chair and pulls the decorative candies off the train. Eats the coal out of the coal car.
Two hours later, while you are in the kitchen area of the Great Room (just on the other side of a half wall that separates you from the table on which the gingerbread train rests), the toddler disassembles the rest of the train and eats more. You decide that you don't want him to have free access to gingerbread cookies for the next week or two. After chipping the icing off it, you give him one piece of gingerbread. You toss the rest in the garbage bin.
Daddy didn't get to see the train. It didn't even last long enough to take a picture of it.
Later the blue candies mysteriously appear on the table.