If you are currently in a work environment where it's common practice for your boss to send e-mails over the weekend just because they have no life doesn't mean you have to be on the clock 24-7 and available for every beck and call. Unless you are in the middle of a “go-live” or there is a critical business issue looming, send your manager a note to let them know you're spending time with your family during the weekend, and you will follow up with them on Monday. Man up! Do you really need to be responding to e-mails and phone calls over the weekend just because your boss doesn’t have a life outside of work?
In the end, you have to make a choice on how to make your weekend/holiday schedule your own. You already give your employer over 2,000 hours each year to perform your work duties and responsibilities. Another 2,000 hours is spent sleeping to recharge your batteries and give your body the rest it needs. I think it's only fair that those last 2,000 hours belong to you and your family.
You - and they - deserve it!