Got any pick-up lines?

OK, this kind of relates to the whole how to pick up friends topic that's been discussed before in my many groups.

Here's the situation. We've been eating regularly (at least once every 2-3 weeks) at a small mom and pop restraunt near us. The owners are about my age and have a little 3 year old girl I'll call C. The mom and I talk everytime she's there (It's usually her DH that's there, who is very quiet Hubby and I just think he doesn't talk like so many of the DH's out there), And if C is there, she and #1 will play together.

Tonight we even had C join us at our table because they weren't done playing when our food came and the mom had a few things she had to do because her and C were headed somewhere. So C happily sat down and had some French fries with us.

Now I really like the mom. In fact she seems to be one of the few normal mom's I've met since moving here, and I'd really like to get to be friends with her. I'm just really not sure how to move from this whole Customer, chat once in a while, to friends. I swear this is almost hard then dating.

Any suggestions on how to not sound too stupid and suggest a playdate or something?????