Thanks, Portia and Phey! We are considering EPGY, but haven't done it yet, and I've been reading up on Math Beast and Challenging Word Problems. So much to choose from!

I've been reading up on as much as I can, once kids are sleeping, etc. What I like about LOF is the way math concepts -- cardinal numbers, sets, parentheses, etc. -- are worked in as he tells the story. *Seems* like a natural way to introduce stuff they don't typically cover at school and that my DS would love.