As a parental control, I'd like to disable the ability to clear the history in Firefox.
Also, how can I have this history be automatically sent to my e-mail address?
You may want to look into a 3rd part parental control program for the emailing of history reports.
Otherwise, Windows 7 has a parental control feature built in. You can read more about it here
You might be happier using your router's firmware to track history and email the logs to you. The browser history is too easy to defeat with portable apps, registy hacks, etc.
Most routers support this feature. If you want to be prescriptive about it, use OpenDNS FamilyShield: set your router to use 188.8.131.52 and 184.108.40.206 as your DNS hosts.