Group that big, I would suggest you call the Caribou Convention Center.
Nice place, pool, bar and restaurant on site. There is the Hampton Inn and Preque Isle Convention Center 20ish miles south of there on the way up. Ft Kent and Madawaska are an hour north of Caribou.
There are smaller hotels in Madawaska and Ft Kent, but it might be tough with a 20 bike group staying /eating together. (Northern Door Inn, Ft Kent)
There are lodges and other small hotels all over the County. ( Overlook in Eagle Lake comes to mind)
Ton of places to stay in Bangor on the way back down, if you are looking to p/u Rt 2 west to NH and VT.
The Four Corners monument is in Madawaska, and in Ft Kent theres a little park with the "End US Rt 1" monument. You could hit them both in under an hour.
RT 1 goes down the east border thru Calais ( pronounced " Kal-us" not Kal-lay" ) then turns up the coast. You could back track to Lubec and Quoddy Head (easternmost point in the lower 48), then go up to Ellsworth. Long rough slog down thru the woods, not a lot of services. I rode it last summer coming back from Gaspe'. Not a howling wilderness, but things are a ways apart down there. Road gets better down by the coast. Rt 9 ( The Airline) back to Bangor from Calais is a nice road now.
Lot of riding up here. If I had a big group coming from away like you have, I would say do the Portland to Caribou ride one day, stay, look around the Valley come back to Bangor taking all day to do it. Stay in Bangor, then you could ride out to Quoddy and Downeast coast loop. Back to Bangor for the night, then out Rt 2 for points west.
Keep in mind that the only HD dealers in Northern Maine are Central Me in Bangor and Ploudes in Caribou. Nothing east of the interstate, but a large metric dealer in Ellsworth. A breakdown will require a lengthy wrecker ride.
Theres 100 diff ways to do it.