I was in the same boat. I have a domain but I was using my work e-mail for everything. I had the wife and kids e-mail on my domain and was using an Exchange server on a home computer for their e-mail. I got sick of the overhead of administering the Exchange server/backups so I did some research and found that you can have Hotmail host your domain e-mail. You can create as many e-mail accounts on your domain as you want once you have your e-mail service configured.
Host your e-mail services
So I moved my e-mail hosting services to Hotmail and then changed the e-mail address associated with my Xbox account from my work e-mail to my personal domain e-mail.
So enter Windows Phone 7. Using my Hotmail hosted personal domain e-mail account, which is by default a Windows Live ID, I signed into my Windows Phone for the first time and had my personal domain e-mail hooked in along with my Xbox Live avatar.
I believe you can set up shared calendars in Hotmail and pull them into Windows Phone 7, but I take a different approach when I need something on various family calendars. BTW, we have 4 Windows Phones in the family. My wife, two kids and I all have HTC Arrive phones.
If I have an event that involves my wife and I, I add it to my calendar and invite her to the event. This way, if the event details change, I can update the "meeting request" and send her an update so she knows about the change. If I have an event where the kids are involved, I invite my wife and kid(s) so they have it on their calendars as well.
This works very well for us and I am out of the business of managing my own e-mail, whether on Exchange server or a hosting company e-mail server. Also any of us can log into any computer and hit the Hotmail website to check e-mail, etc. There is also a Hotmail connector for Outlook. So if you are a diehard Outlook user (I'm not anymore) you can sync your Hotmail account with Outlook. This includes received, sent, deleted mail items, contacts and calendars.
Sorry for the long winded response and hope this helps.