An Enlightening Trip to the Mall

Every Monday Greg and I go to the mall. We meet another SAHM and son for a little shopping, a lot of chatting, and tons of socialization. The mall has a great new kids play area. Everything is fall safe: the floor is spongy, the climbing equipment is soft and rounded. Greg looks forward to the mall from Sunday afternoon and talks about it all day Monday. He loves seeing his friend and playing. Yesterday didn't go so well though. When we got there I chose to sit in a new spot. Greg walked to our old spot and sat down. He took off his shoes and put them in the cubby-hole where he always does. Then, instead of playing, he came and sat in my lap. When his friend got there Greg had trouble sharing. He was fussy and crabby. We even had to leave early due to a giant temper-tantrum.
My friend asked me "Greg thrives on routine, doesn't he?" The answer is a resounding yes! It took Toby and I awhile to figure this out. I don't know why, I'm the same way. When things don't go as I expect, I get crabby. Greg had a lot of problems sleeping until Toby and I became disciplined enough to get him to bed at the same time every night. It changed Greg's whole temperament. He would wake up in the night unable to sleep and go through the days in cranky exhaustion. Greg also loves music; the predictable repetition of the beat and melody delights his senses. He learned the actions to "Twinkle, Twinkle Little Star" by 15 months. I always attributed my annoyance with a break in routine as control issues (and I'm sure it is in part), but now I see that it's part of my personality. Greg and I love routine!
This leads me to a whole list of questions: How can I help him to adapt to changes in routine? How can I respect his need for routine? What does this reveal about God's purpose for my son?