In the past 20 yrs.... things change... yet stay the same. Good suggestions for Vt and NH highlights have already been made. If you go to Americade, suggest rte 28 west over to 30N to 3 west to Watertown and the 1000 island area. Rte 3 So of watertown along the lake to any of the smaller roads down to the finger lakes region--great twisty roads to enjoy! Maybe to cooperstown or watkins glen...
cant give too many suggestions for PA other than to try and avoid the metro areas and the superslabs.... they are murder in cages, and worse on bikes. (they actually have agressive driver area ahead signs!)
If in PA...gotta go to hershey and Amish country... From there, DC is reachable by some smaller roads.
As for tips for black flies.......... hope for a dry spring, and drive with your mouth closed, even if you have a full face helmet. I know, tough on a wing with our smirking smiles, it takes a couple of miles, practice, and about two or three mouthfuls of the little bas#$!ds to get the nack and importance of it......Also the driver can duck behind the windshield... your rider will not be happy.
Pick up some blackberries and practice spitting out " the crunchy parts" thats about the closest I can suggest. unless they go past your teeth and into your throat..... keep a bottle of water handy.
They are normally in HUGE swarms which you will see hovering over the road... sometimes you can duck and weave......And always worse as the heat of the day increases and towards dinner time. While riding any bug repellants dont really work, but if you are going to be camping, liquid repellents with high levels of DEET are required. Skin so soft has mixed reviews...
Hope you have a good trip!