JsMom,
I have inflamation in my gums and mouth as well. Some mornings I have difficulty brushing my teeth because I am so sensitive. My uncle who also has Crohn's experiences gum inflamation as well. I thought I was crazy until my uncle reminded me that Crohn's can manifest in the mouth. "Sensitive toothpase" has been helpful. Hope your son feels better!
I have suffered from gum inflammation for a long time, even with ulcers in my mouth. Sometimes my gums are swollen and red and even have red nodules on them, which didn't happen until the crohn's.