Sounds like a reasonable route going out. Route 2 is a nice enough road. For the section between Burlington and Barre/Montpelier where it parallels I-89, I would suggest taking the Intestate as it's generally a little nicer and quicker and the scenery is hardly different. (For a good bit of that distance the two roads are separated by a Jersey barrier or not much more.)
I would consider a detour through the New Hampshire white mountains. There are a few different roads through there, and all are generally good roads and beautiful. My favorite is probably the Kancamagus Highway. The Conway/North Conway area on the eastern side is usually pretty slow going and crowded (it's quite a commercial strip, lots of outlet stores and so forth...which is either exciting or dreadful, depending on your temperament).
The Fairbanks Museum in St Johnsbury, VT is worth a visit in my opinion. It's a very traditional, mostly natural history museum, which hasn't changed a whole lot in many decades. In some ways it's as much a museum museum as a natural history museum. Down the road a bit the Athenaeum (public library) has a fantastic little art gallery. Both of these institutions owe a lot to Mr Faribanks and the success of his scale manufacturing many years ago.
Another museum that's only a little out of the way is the Shelburne museum in Shelburne, VT. This is a very eclectic museum, a quite large and spread out space, and I'd suggest devoting a whole day to seeing it. Not too far is the Lake Champlain Maritime Museum which has good reports, as well.
If you have certain sorts of activities or sites you're particularly interested in, or certain sorts of campgrounds you prefer, it would be helpful to know for making relevant suggestions. The Vermont state parks are generally well-kept and well-run but the campgrounds are fairly primitive--no hookups, dirt roads, often many fairly small (but private) sites, etc. The NY state parks I've been in have been quite decent, too, and tend to have slightly more modern campgrounds.