This post lists examples of prospective buyers for children's books. This is by no means an exhaustive list but should stimulate your thinking to find new places in which to sell your book.
Expand your approach to book sales to include retailers other than bookstores (including online retailers). The more strategic you are about where your book is available, the more likely your target buyers will be to find and buy it.
There are two ways first-time authors can plan their book marketing activities. The first is discovery-driven planning, which evolves through trial and error. A second technique views planning as narrative, conducted as you would when writing a novel.