People come to yard sales looking for rock-bottom bargains -- a $5 stuffed toy doesn't quite fit the bill. Chances of a beanie baby collector happening by are slim. Additionally, you run the very real chance that children will pick up and play with the toys, and they could be soiled and lose value.
Instead, I'd suggest you put them on ebay. You'll be able to market your beanie babies to a much wider audience, and you're likely to make much more money.