LOL We fed them chicken nuggets and pizza!! We didn't know at that stage. We actually only changed their diets because gluten free and dairy free is sometimes helpful for kids with autism (the younger child is autistic). It was only after we saw how helpful it was that we began investigating and found that both children had real problems with it.
Most parents on this diet that are at your stage, though, use rice cereal and puree their own fruits and veggies. You really have to be vigilant about reading labels ... I've found whey as an ingredient in canned chicken broth and applesauce!!
When they're ready for cheese, try this: http://www.daiyafoods.com/
It is, without a doubt the best non dairy cheese.