Also, once you get to Lake Champlain, the routes are exceptionally well marked. Lots of bike signs. It's hard to screw up once you get there.

Anyway, as for the route, I recommend keeping as close to the Hudson river as possible until you get to the Troy area and the area immediately north. I recommend taking Route 4 from there.

Here's a useful map for biking near and around Lake George in NY:

http://www.lakestolocks.com/map.php?region=3

Once you cross into Vermont, I recommend getting on 22A in Fair Haven and riding it until you arrive in Vergennes and then riding Route 7 (a very well marked cycling route-- even though it can be busy during rush hour, I believe it to be fairly safe until it gets a little hairier in South Burlington)

Also, apparently I forgot that the ferry from Charlotte drops you in Essex, NY. You can ride south to Westport from there on 22 South (a very beautiful, rolling route along the Lake)

Another option you have for getting to Burlington is to ride 9N along Lake George past Ticonderoga, NY and then when 9N breaks with Route 22 in Westport, NY, continue on 22 all the way to Port Kent where you can take the beeeaaautiful ferry into Burlington across Champlain.

Anyway, food for thought! I'm envious that you've got the stamina and ambition to do this!