Have you thought about something like a
lazer or a flying scott? A small boat will teach you a great deal about sailing, more that most pocket cruisers. The kids will have an opportunity to learn and decide how much sailing will come into your life. Also, think about chartering a bigger boat with a captain, taking the family and see how they enjoy it. For the lake, a smaller boat capable of overnighting would make sense and they can be had for under 5k.