I would suggest you to first of all be sure to list your company in BouncerLand's rental directory at
http://www.bouncerland.com/addrental.php , we get lots of rental requests every day, so that's one good source of business for you
About email:
I don't think email marketing is something good for local businesses at all. The problem is the response rate to marketing emails is VERY low and when you are talking about a local business (and add to that the "specific niche") you end up with a very low amount of recipient .. so getting a response from your email campaign becomes a very rare chance. Moreover i don't think any bulk mail company maintains an accurate list of specific local businesses.. they rather have huge lists of nationwide niches.
If, however, you still want to try the email method - it's better for you to go over the search engines and search for those local daycares, find their email addresses (or contact forms on their websites) and send them PERSONALIZED emails. You will get much better results when your emails are personlized because people tend to not read "template-driven" emails.
A better alternative to emails may be posting an add in local newspapers and maybe making some flayers and handing them over to those specific businesses (day care, etc).
Regards