Looks like you got lots of suggestions. Having lived in that area, and having seen everything suggested, I would put these on the must see: Blue Mountain Lake Adirondack Museum, Whiteface Mountain (drive up on a clear day), Finger Lakes area, Watkins Glen, Letchworth State Park. I also agree that the Thousand Islands (do the boat tour and antique boat museum) are great, but often missed. If you drive through Old Forge, be sure to stop at the hardware.
It all depends on what type of fishing you are looking for. You will find special trout water on the Ausable River near Lake Placid. There are lots of places to access creeks and rivers for trout fishing, and places to rent canoes for lake/pond fishing throughout the Adirondacks. Some of my favorite places are more off the beaten path like creeks that feed the Moose River and the Salmon River in the Tug Hill region (do NOT venture into Tug Hill without very good maps, since you do NOT want to get lost in the 46 corners area).
I try to avoid I90 (NYS Thruway) because of tolls, and take it only in hilly areas. The drive between Old Forge, Tupper Lake, Saranac Lake and Lake Placid should not be missed. Pretty drive (not towing for us anyway) from Lake Placid down 73 through Keene Valley. Sampson State Park is a good location for Seneca Lake wineries. Drives around any of the Finger Lakes are very scenic.
NYS DEC parks in the Adirondacks are no hookup, so that might influence where you want for ADK base camps. Given the time of year, it will be getting cool further north, so you might want to visit north first, then south (where you should find Concord grapes in season at roadside stands, and maybe some early apples).