It sounds like a consult with a dietician or paed would be a good idea, rather than chopping and changing or guessing.

I was given alot of soy as a child, and I don't think it did me any favours (hormonally). Even if my boys could drink soy (they are both dairy and soy allergic) there is no way I would give it to them. I'm not against all soy products at all, soy in more natural forms is very healthy, but I personally wouldn't be letting a small child drink soy milk. But that's just my opinion, and I'm no expert .

Most rice milk is calcium enriched, so that's a start. Sure, it's not the most nutritious milk going round, but there's other ways of filling nutritional requirements than milk . It's just nice to have a milk replacement for cereal etc. Oat milk is also nice.