Is there any possibility of you inviting her child over to play and have tea with your child?
Can you stand by her and getting chatting whilst waiting for your kids to come out to help break the ice? If so and you know she's single then just go for it and ask her out, to the cinema or something. She will be flattered I'm sure. The worst thing that can happen is tthat she can say no. She could well feel the same way about you and doesn't know how to approach you. You've nothing to lose. Good Luck!!