Salvation army ....
In all reality you can spend $10 on a pair of shoes up to $300, and that's really for sneakers - shoes can go well above it, depends.
You need to figure out what the kids want, then figure out if it's in your budget (try shopping.com as a great comparison site), then make sure you have the right sizes. Got 3 kids (2,5 and 9) and the younger ones have luckily been able to re-use the hand-me-downs as the 9 year old grew out of his shoes so quickly they hardly had any wear / tear on them. The sneakers were different as those got beat up a lot more than the shoes.