John,
JFK and Laguardia are in NYC. That's 5 hours away. We are WAY up North! Darn near Canadian eh! Actually my fathers side is Canadian. Bob was right, Burlington is the largest and closest airport, but you can also grab a hopper from there to Clinton County Airport which is right in Plattsburgh itself. There is no car rental there, but several down the road on RTE 3. I would be happy to pick you up if you decide to do that. If you fly in to Burlington, there are rentals there. You will also have to take a ferry across the lake from the island, which will give you your first good look at Champlain as you will also have to come down the Sand Bar bridge to get to the ferry. The island, 1 of about 120 on the lake is about 25 miles long and 10 miles wide. Hope that gives you an idea of the size of the lake. For a whole family vacation, my recommendation is to stay over in Burlington after the rally. There is much mort to do over there. It's only an hour at most from Plattsburgh. If you need any more info, feel free to e-mail me.
Rob