It's not that they sleep that soundly but our kids have always enjoyed sleeping as the boat gets moving. I like to get up early, especially on the water so after making some coffee, (take the dog ashore) I'll often raise the anchor and get underway at first light. That's often made a difference in how far we'd go that day.

And while we don't do it often, we've had good luck with a well planned overnight to cover the distance to say Cape Cod from Maine, and back. That has enabled us to enjoy a two week vacation down that way a couple of times with great success. It's not always an easy passage but I think everybody feels pretty good having accomplished it. I also like Larrys idea and will move the boat myself occasionally. We're not big fans(as a family) of "moving the boat" as opposed to enjoying sailing an area at our own pace, but we'll do it to sail and explore new areas.

To answer your specific question, 20 to 30 miles, depending on conditions of course, is pushing the envelope between enjoyable coastal sailing and, moving the boat for us. That gets us into an anchorage early enough in the day to get ashore and do some hiking and exploring. If we're where we want to be, a nice sail of a couple of hours is hard to beat.