Lightning as a Family Daysailer?
Go for the Lightning. The cockpit is big enough to allow the kids to invite friends, and the existing fleet will provide boats for you to buy AND a market if you decide to sell later. Racing can be a good way to meet new friends and keep daysails from becoming boring to soon-to-be-teenagers. The large sail area is great for keeping moving when the wind is light, and stunning performance if it picks up (planing with just the main&jib is a real trip!!) The hard-chine hull provides excellent initial stability, so you have enough time to react to puffs (or lulls) that lakes are notorious for. (Round-chined dinghies tend to be crewed by guys in wetsuits.)
I''ve found Lightnings very comfortable to crew on because of the seats inboard (use the coaming for a backrest), the wide side decks (don''t cut off circulation) and the nice, flat foredeck. (great for stretching out in the shade of the jib if there''s no breeze), Lightnings are also beautiful to look at. Few boats that will meet your needs so easily can make that claim as well.