I have head that it can even act as a protein replacement in a vegan diet
Quinoa has all the amino acids of a complete protein and I think it is the only non-meat source that has this, so yes it is an excellent source of protein!
Ack I really need to get into making more quinoa! My naturopath had showed me a book she has called 365 Days of Quinoa or something like that. I think it takes some getting used to but if you find recipes you like then you start to love it.
I have used the flour in baking and DH has used it to make quinoa flour tortillas, since it is gluten free. It is a tricky flour because it has a strong flavour, but I have a chocolate cupcake recipe that uses it and the chocolate masks the flavour and it's quite good. Not that you'll be giving DS any cupcakes anytime soon! lol But just so you know it is quite versatile.
Can he eat rice? DS1 was handling it fairly easily by that age. It's a similar texture to rice, but much smaller so would probably be easier to manage. I'm not sure though how he would be if he's not great with textures yet.