Thanks for the Aerotechdesigns recommendation! Their stuff looks great and comes in appropriately small sizes.
There's really no Walmart near where I live, but I thought they sold mostly dollar store stuff anyway? Interesting. And for some reason I completely forgot that one of the LBSs near me is managed by a guy with kids the same age as mine, so I will also ask him.
Still interested in any further recommendations, especially for reflective vests. (At least 90% of our riding is on the street, and even with the flag on her tag-along I'd like a little more visibility.)