Acadia is really great to ride. But if you have the time try Sunrise Trail. It's a packed gravel/dirt trail that goes from Ellsworth up to Calais. That's about 85 miles one way. Also there's several cutouts along the way so you can head into one of the towns along the route and grab some lunch. It's doable on any type bike, but it works out best with a CX bike or at least wider tires. You share the trail with ATV's. I've ridden it several times during the week and never encountered another vehicle. http://www.sunrisetrail.org/ Weekends do tend to be busy with ATV 'tour groups'.
If the ferry from Bar Harbor to Winter Harbor is still running (June-Sept) do the park loop, catch the ferry to Winter Harbor ($30 round trip), then do the Schoodic Point Loop. Stop by Fisherman's Inn to grab some lunch.
If you need more info let me know. I've been going there for several years and know 'Down East' pretty well.