Broken routine = meltdown

Oh boy the meltdowns! Every weekday when I take the kids to the in-laws while I work, Michael has a set routine. I get him out of the car and he runs to the door and waits for me to get Rory. Then we go in the house and he sneaks around the corner by the kitchen until he decides it's time to go in the room. He does this the exact same way every day. If something is different about this routine, his world collapses. This morning when I went to drop the kids off, my father-in-law decided it was a good idea to open the door when he saw Michael approach it. By the time I got to the door, Michael was in complete panic mode and crying. He was desperately trying to close the door and reset his routine. But by that time it was already broken. I closed the door hoping this would reset it for him but it didn't. He ran off and tried to run off the driveway. I had to go catch him with Rory in my arms. I had to drag him in the house, kicking and screaming. He kept going to the door, trying to open it saying "OPEN DOOR!!!" I had to finally sit down by the door with him and give him deep pressure hugs for a few minutes until he finally calmed down. At that point he decided it was okay to go on with the rest of the routine from there. He walked over toward the kitchen and hid around the corner in his normal fashion. Ah the joys of my daily life.