Unfortunately, you probably should be supplimenting, unless you are relying very very heavily on goats milk. Rice milk contains no calcium on its own. It is "fortified", which means calcium is added. Unfortunately, this calcium suffers from the same problems as many supplements, it is poorly absorbed by the body.
Calcium is contained in other foods, but kale and other dark green leafies aren't generally popular with the toddler club. (iceburg and other salad lettuces don't really contain significant amouts of calcium) There are other sources (that are about as kid friendly), but they are pretty insignificant unless eaten in large quatities.
I would say better safe than sorry and go ahead and add a suppliment to their diet. I'm in the same boat, we are doing GF/CF. Good luck, the benefits are usually worth the frustration.