Oh man, Autumn in the Northeast is fantastic. All the places I can think of are best served by being active, but if hubby has health problems there are usually other options.
Here is my opinion:
Catskills. Or, rather, Shawangunks. Depending on how ritzy you want to be, spend a night or two at the Mohonk Mountain House outside of New Paltz, NY. It is a superb hotel/restaurant with a beautiful view of the cliffs that make the Gunks a destination for Mountain Bikers, hikers, and rock climbers. If you're into road riding, take your bike for a spin up the monster hill under the cliff. If you have trail bikes and will be bringing them, you have your choice of more challenging mtn bike trails or the Undercliff Road that takes you past the superb climbing of the Trapps. The trail is not very challenging, flat, and is several miles long so you can take it for as long or as short of a trip as you like. There are also mtn bike and hiking trails that start from the Mohonk Mountain House. I would recommend going in October to catch the best of the leaves changing and at least take a nice hike down the carriage road to check out the view of the trees and the unique atmosphere that makes this one of the most interesting places I have ever been. You will see families from the city out for walks, Orthodox women out for spins on their bikes, climbers and bikers and hikers intermingling in a very interesting way. I also recommend a trip to the Mohonk Visitor Center to learn about the land around there. If you want something less physical, you have that too! There is phenomenal shopping and dining in the quirky town of New Paltz (home of SUNY New Paltz... so there's good people watching too). I recommend specifically a dinner at Bacchus, especially if you like really good burgers and an amazing selection of beers from around the world. If you're into wine, there are several vineyards located around the area. Simply follow the wine-trail signs to take you to small owner-operated vinyards where you can get good tastings and sit outside to enjoy the scenery. I believe there is also a ton of antiqueing around the area if you are into that. In addition, October is a wonderful time to visit the Gunks because there are a large number of orchards that will be hitting apple-harvesting time just around then. You can pick your own apples, taste homemade apple cider and apple cider doughnuts. The Honey Crisp varieties are to die for!
If you wanted further north than that (the Gunks are about 1.5 hours from NYC) I would head to Vermont or even New Hampshire. The town of North Conway, NH is pretty awesome, and has some GREAT outlet shopping (Pearl Izumi has an outlet shop up there....mmmm) but I have never done anything up there other than outlet shop and rock climb or hike so I can't help you there with recommendations of non-physical things to do.
But, as you can tell, I'm a regular at the Gunks, so if you are interested in visiting there, just shoot me a PM and I can give you some more info if you need it.
K.