That brings up another worthwhile point... None of your options are purely self teaching. I would consider Singapore, MEP, and Miquon to all be conceptual math curriculums. One is Asian, one anglo-hungarian, and one constructivist new math. They all take a slightly different approach that is different from traditional US texts. I have no idea what is or was trad in NZ. Whatever you chose, I would try to understand and follow its approach.
Singapore is very big on number bonds, mental math, and bar models. Some parents ignore this and "supplement" the books with more traditional algorithmic instruction at an early age... I think this misses the point. The mental math elements are a huge strength of the program... it doesn't matter that the standard algorithms are introduced in year 2 in SM and year 3 in MEP. The number sense built prior to that is a huge strength of the program. I don't think you need the expensive Home Instructor Guides(HIG) but taking some time to understand what SM is trying to do would be worthwhile.
Many people like Liping Ma's "Knowing and Teaching Elementary Mathematics". I wouldn't buy it, but it well worth reading if you can get if from the library.
