Well...30' in a nice beamy boat like a Catalina 30 will be crowded but doable for a week for parents and 2 kids. You can single-hand one easily and frankly, there is not much diference between single handing a 36 vs. a 30 if the boat is set up right. Despite my own center cockpit preference and the privacy it affords one with a rear stateroom...for single handing an aft cockpit works a bit better as you come into the dock. The main thing you'll need to adjust to is the different weight and momentum between power boats and 30-36' sailboats as you come into the dock. Buy some big fenders!
Out on the lake, my own experience is that bigger boats are easier to handle as they heel less and are generally well set up with whees, autopilots and big winches that make it pretty easy to manage things.