If there's one thing I've learned about selling children's clothing at yard sales, it's to make sure to list those items (including whether boy's or girl's clothing and the sizes) on the yard sale signs. Lots of people will come out to yard sales, but by advertising the clothing and the sizes, you will end up getting people who would not ordinarily stop. Since you have some great brand names, you could also include those on the sign if you wanted.
The main thing is that most people who go to a yard sale tend to go every weekend once the weather turns nicer. Those are the ones that will typically look for specific items or for collectibles. To entice those that don't normally do the "yard sale thing", you need to let them know exactly what they will be missing out on.
It's worked for me in the past and I've sold more children's clothing than anything else I've tried selling. While I can get rid of "big ticket" items like furniture, tools, etc. and smaller things like books and videos, clothing is still always my #1 seller.