Here are some photos of all the ideas I mentioned in the planning stage.
The children entered and were directed to the front desk/ticket counter where they received their ticket to board
The "blizzard" concept realized: (I will provide a tutorial soon)
The guests walked through 3 doorways decorated this way as they entered the "train" where the conductor punched their ticket.
This is what the children saw as they entered the "train"
Twinkle lights strung across the ceiling held silver strands of "icicles" to give the illusion of falling snow.
They entered the child-sized buffet line through this train tunnel.
The centerpieces were changed a bit as we realized they looked better nested in a bowl of snow. We snipped a bit of pine branch from outside to add some dimension and color.
As the soundtrack played "Hot Chocolate!" silver urns of it were wheeled in and the hot chocolate bar, complete with bowls and bowls of toppings, was unveiled.
Check out this edible train that held the cheese and fruit on the buffet! The chef constructed it from melons, pineapples, and various other fruits and veggies. Piled around it were mounds of cheese cube "snow".
The children occupied themselves with cookie decorating and Polar express activity sheets before and after the meal as well as writing a letter to Santa. They decorated the envelopes and sent them away in the mailbox provided.
Finally, they settled down to view the movie as they cuddled up with pillows and blankets on the floor.
As the end of the movie approached, each child was given a silver bell (see the planning stage above), gift wrapped in candy cane striped paper just as Santa's gift to the boy is revealed on screen. Each of them held the bell up to their ears and proclaimed, "I believe" which was inscribed on the tag. I recommend waiting until the end for this as we did, because it all fell apart at this point! Kids began to run around ringing the bells but the evening was nearly over and it was a good transition to get ready to leave.
I hope this helps you plan your own Polar Express Party!