The Glenns Falls Lake George bike path is nice - I rode it last summer.
You may want to check out this que sheet - you could pick it up in Lake George.
Route 9 is a very good road but there are a lot of very good roads off of Route 9 as well.
There is an ultra-marathon route that goes from Schuylerville to Montreal but it goes through Keane Valley - that is going to be pretty steep over there. I would stick as close to the lake and canal as I can. You will also find a Stewarts shop in just about every town - very good supplies for the road.