We live in MA, so we've visited VT, NH, ME often, but never exchanged points through RCI...so not sure where you could stay.
We haven't stayed in Smuggler's Notch--but we have stayed in Stowe, VT. On the way to Stowe, in Waterbury on Rt. 100--we like to go to the Ben & Jerry's Ice Cream Factory (small fee, includes ice cream tasting), the Cabot Cheese Factory Store (free tastings of cheese, and other items), Lake Champlain Chocolate Company, the Cold Hollow Cider Mill Store (free tastings of mustards, jams, cider, etc.) and next to the Cold Hollow Cider Mill is a winery (small fee for tastings.) Stowe, VT has the 5 mile recreation path that you could bike/walk on--starts in the town center. We went to Stowe over July 4th one year and they had a really great 4th of July celebration on a town farm area--lots of free kids activities, pay food, and fantastic fireworks. Being in the Stowe area, you're not too far from Lake Champlain if you wanted to take a boat ride there, and there's also the Barre Granite Quarry the other direction.
The White Mountain Region of NH--North Conway, and Jackson area are very nice. Kids theme parks open from Memorial Day to Columbus Day--Storyland in Glen, NH and Santa's Village in Jefferson, NH. Lots of hiking trails of all abilities in the White Mountains, as well as the driving road or tour up to the top of Mt. Washington. North Conway has Outlet Malls if you like to shop. (NH has no sales tax.)
Southern Maine--As a kid, I visited Ogunquit/Wells beach areas often. We take our kids to Old Orchard Beach--Palace Playland is by the pier and has arcade games, and rides. All ocean water in Maine is cold...especially depending on where you're from. Growing up swimming in Maine water and remembering how quickly my ankles went numb, we try to go around Labor Day weekend when the ocean has a chance to warm up. Mid-coastal Maine, has Bar Harbor which is nice to visit. Acadia National Park is located there. As it's a 5hr drive from where we live, we've taken the kids once...about 8 yrs ago.
If you find other places in New England in the RCI list, those of us from New England may be able to tell you more about them.
I hope you enjoy your trip. We do love the fall foliage here!