I'm in the same....er...boat! I could never make the numbers make sense for a second home near Chicago, and - truthfully - could never figure out a place I would want to go for most vacations....I like the variety of new places.
Plus the Baby Boomers got all the nice nearby Lake Michigan places (New Buffalo, St. Joe, South Haven, etc.) and little lake areas (Lake Geneva, WI or Culver, IN) 20 years ago and the prices are now crazy expensive for beach access. The best small lakes (Torch, Charlevoix, Glen) are 6+ hours away and so no good for a weekend.
My youngest is 8 and comfortable in the water, and I grew up sailing so I bought a Hobie Cat and put it on the Beach for fun weekends in Wilmette, IL, and either charter larger boats
http://www.moorings.com or go to tropical sailing resorts
http://www.beyc.com.
Since you want a powerboat, you might want to charter a boat first just to make sure everyone enjoys it (Moorings rents powerboats - and it is an easy sell to a spouse for a shakedown cruise in, say, the British Virgin Islands or the Great Barrier Reef). If they like the overnights, your plan sounds good. If not, you might want to just get a speedboat for day fun (or even rent one for a week or two - they do that up near Traverse City and will even deliver it and some jetskis to a nearby lake home rental - great fun and no hassle).
Don't know enough to give advice about the powerboats you listed. But, in any case, good luck with your plan!