Starting from Portland, try to see if Amtrak will allow bikes on the train that goes to Portland.. see if you can get your bikes there all the way from VA.
As far as bike shop, yeah, you can certainly send it to a bike shop, you just need a recommendation (which not being a resident of Portland nor have I ever spent much time there as a cyclist, I can't help you here) but it's not too uncommon for people to ship bikes to a bike shop to be picked up. But obviously would be nice to see if you can bring it with you.
Rt 1 is very busy in the summer, frankly, it is nice but the traffic is sometimes bothersome and between Bath and Brunswick, Rt 1 is a divided highway and bikes are illegal anyway.
Going inland towards Sebago Lake from the Kennebunk area is nice, I've camped at a Family and Friend's campsite on the western shore of Sebago Lake once, it's a nice private campsite. Just be prepared to share the campground with Huge Monster RVs while you sleep in your tiny 2 person hoop tent. :-P (you get used to it!).
You have a lot of time there but you will have lots of places to check out, Camden is a pretty neat place, if you have time, some nice hiking in Camden Hills (megunticook, battie). Of course, Camden Bay is nice and you can get cutter rides and stuff from there.
You might be able to get a bike suitability map from Maine's DOT (MDOT) but I can't really find a link anymore, but I got one awhile ago, perhaps email MDOT...