As a starting point, I'd suggest:
Fri Aug 24 -- head south from Portland to Kennebunkport -- with a one-hour drive, I'd hop on I-95 southbound instead of messing around with local Friday night traffic on US Rt 1.... get off at the Kennebunk exit and follow state and local roads to Kennebunkport.
Sat Aug 25 - Sightseeing Kennebunkport, Ogunquit, York (if you get that far south).... you could either spend another night in Kennebunkport (depending on how long a day you want to spend on the southern coast) or book somewhere in Portland-South Portland to give you a jump on Sunday's driving....
Sun Aug 26 -- Travel day -- Kennebunkport or Portland areas to Bar Harbor/Acadia National Park. Given that Sunday is part of "weekend traffic", I'd be tempted to take I-95/295/95 to Bangor, I-395 to Brewer, US 1A to Ellsworth and Rt 3 to Bar Harbor just to get to Bar Harbor as quickly as possible without wasting time in traffic on Rt 1. Stop at the National Park Visitor's Center on your way into town and let them help you maximize the time you have available for seeing Acadia. Spend the afternoon seeing as much of the Park or Bar Harbor as you can. Overnight: Bar Harbor or somewhere else on Mount Desert Island... several communities within easy driving of the Park.
Mon Aug 27 -- Full day sightseeing/touring/boat cruising etc. Acadia National Park and Bar Harbor area. Overnight same place as Sunday Aug 26
Tue Aug 28 -- Head south along the coast (weekend crowds are gone now).... Rt 3 to Ellsworth, then US Rt 1 south. Stops at Penobscot Narrows Bridge Observatory and Fort Knox State Park just south of Bucksport; Mt Battie Auto Road in Camden Hills State Park just north of Camden on Rt 1; Camden Harbor waterfront; Rockland Breakwater Lighthouse; perhaps Farnsworth Art Museum in Rockland or Owl's Head Transportation Museum in nearby Owl's Head. Overnight Rockland or Camden.
Wed Aug 29 Rockland to Boothbay Harbor with possible stops in Damariscotta (nice little coastal village); trip down Pemaquid peninsula to Pemaquid Lighthouse Park; possible detour onto Rt 129 for lobster on-the-water at Shaw's in New Harbor or Muskongus Bay Lobster in New Harbor; Boothbay Harbor harbor area and downtown; maybe a harbor cruise; and sunset at Ocean Point (end of Rt 96) in East Boothbay. Overnight: Boothbay Harbor
Thurs Aug 30 Rockland to Portland -- possible stops along the way include Admiral Peary Arctic Exploration Museum at Bowdoin College in Brunswick; L.L., Bean multi-store campus (and other shopping including many outlets) in Freeport; Portland Head Light lighthouse in Cape Elizabeth (very short drive from downtown Portland); maybe an afternoon ride on a Casco Bay Lines ferry to one or more Casco Bay Islands; and strolling/shopping and definitely dinner in Portland's restored Old Port District. Overnight: Portland or South Portland
Fri Aug 31 -- Leisurely breakfast before heading to the airport for flight home...
Most of the places/attractions mentioned above can be Googled for more info....