I don't think the calcium supplements and calcium-fortified rice milk are really doing the trick for him. I've been trying to make sure he eats calcium-containing dark green veggies every day, but that can be a challenge for a 5 year old. I recently found a source of raw goat's milk and tried it to see if it caused the same reaction that cow's milk does. And lucky us! No reaction (so far)! I am so relieved to find a better substitute that is more nutritious than rice milk, and I will be able to get cheese as well. He is hesitant to try it, but we have slowly been working it in.
I don't have my hopes up just yet though. We had success with soy milk for about a month before he started reacting to that after switching him off cow's milk so the jury is still out. But the most frustrating part is that his little brother (10 months old) does not tolerate the goat's milk so I'm still stuck using rice milk in a lot of my cooking. :(