I am the worlds worst PPC marketer however I would target the time that your demographic is likely to be online... i.e moms after school starts and before school finishes and them maybe in the evening for a few hours.

We do "day parting" on some of our larger campaigns and base our decision off of "actions"...(the ones that have enough data to allow us to make an informed decision on turning on/off certain times). Here's what I'd recommend:

1. Log into Google Analytics
2. Make sure you have eCommerce enabled in GA, or at least Goals setup in case you're not selling anything (ex. a Goal can be used for email captures)
3. Make sure to use the Advanced Segments feature and select "Paid Search Traffic"
4. Once you have enough data around these actions (50,100+ sales or goals) the go into your Goals tab >> Total conversions
5. In the upper right hand side, click on the hourly or daily icon (this aggregates your goals for each hour of the day)

You should now be able to see at what time of the day you're converting. Most people make the mistake of looking at when traffic is coming to their site, when you really want to focus on conversions. You can then use this data to setup day parting in Adwords.

Hope this helps!