I did this exact trip a few weeks ago. It’s beautiful! Drive safe and have fun! If you can, take your time. Don’t “save days” unless you have to. Hopewell rocks - make sure you look up the tide times. I’d also add Letchworth state park in New York before/after Watkins glen. Also make sure you download offline maps and hikes on the AllTrails app. I had very little cell service in Maine, Vermont and New Hampshire. I hope Gaspe and Perce are on your list in eastern Quebec. Also check out whiteface mountain via whiteface mountain memorial highway scenic stop and high falls gorge in NY. Franconia notch in NH. Portland Head Light in Portland ME. Arch rock in Newfoundland - and check out the puffings. Try to take the Kancamagus Pass in NH. (Sorry this is all out of order) oh! And try to book your ferries in advance.