I'm hoping to do an Adirondack trip too, not necessarily on the official routes...
You can ride just about everywhere in the 'Daks, and you'll be on a good road with shoulders or low traffic, and have lovely scenery. I'd especially recommend NY 3, NY 28N, NY 30, NY 73 through Keene Valley (five stars for this one), NY 86 and NY 8. River Rd. along Franklin Falls Pond is beautiful. Route 9 can be a bit trafficy but is still a nice ride. NY 28 has narrowish shoulders in places and traffic around Old Forge, but it's all still a decent ride.
We rode a beautiful loop around all three Saranac Lakes using Forest Home Rd., NY 30 and NY 3. I've toured the AC route and highly recommend it - many of my recommended roads above are on this route. Some of those recommended roads are also on the Northern Tier. I would like to check off riding all the state and county roads in the park.
We're going to Lake Placid in a couple of weeks, with the express objective of cycling up Whiteface Mountain. (My wife likes climbing.) You can ride from Wilmington (8 miles) or from the toll booth (5 miles), it averages 8% grade. The lower half has some steeper sections so we're going to ride from the toll booth. Talk about "earning the view", it's stunning.
You can also plan stops with short hikes off to see waterfalls, and some of the high peaks can be hiked as day hikes.