Loualfr - I'm married with three children ages 10 and under. We've considered Sailtime in the past but note that, in addition to the concerns identified by JohnRPollard, synching up appropriate sailing weather for my wife and kids with scheduled time on the boat is often a challenge. If there is a nice day with 15 kts of breeze, we want to get out there (with kids). That may not be a scheduled day with Sailtime. The flip side is that you may find that on your scheduled day with Sailtime it is blowing 30 kts with 8 to 10' seas. Less than ideal for three kids.
We sail a Beneteau First 265. We bought it used 3 years ago and have been happy with it for its intended purpose. It has a diesel and modest accomodations. We've done weekends aboard without complaints as to size and space. I don't think you need too large of boat to accomplish your goals and, as such, believe you're on the right track thinking about a well-maintained but used catalina/pearson in the 30' range. I suspect that with the right boat, your full year's cost of ownership will be less than the $5,000/season they get around my area for a Sailtime share.