So at the party we had it set up to be like the Island of Sodor. We put down duct tape railroad tracks, made RR crossing signs, and each of the games had a Thomas character with instructions for what to do.
Of course the favorite activity was the jumper (thanks G&G!), and then anything involving getting wet. Cranky dropped some cargo into the ocean so the kids had to help fish it out, and then they went for a washdown! Josh strung our sprinkler up in the air, and the kids just thought it was grand running through it. You can see Wyatt wasn't quite happy about all of it!