We were there in August 2006, the weather was perfect, the kids were at a great age, and it was beautiful!!!! I rate it as our best trip as a family. We stayed at Mt. Desert Narrows II Campground, on Rt. 3 when you first get on the island. It's a private campground, very nice, full hookup, and most of the sites have a view of the bay. We did like it, but we tried to move into Blackwoods because it we georgous, but it was all booked up for the entire time we were there. I think there is a bike trail through Blackwoods too? If you can get through your time time there without hook-ups I highly recommend! We also drove through the other state park campgound (I dont recall the name, but there are only two), and it too was very nice, although not as nice a Blackwoods, in my opinion.
There is soooo much to do in Acadia NP, especially if you like to be active when you camp. The carriage trails are a must, and a must on a bike, absolutly beautiful. If you dont ride very often some areas can be a little hilly. My wife and kids wouldnt/couldnt ride the whole thing but I did all the trails. I think there is 48 miles of trails??? dont quote me on that, but quite a few miles.
I dont recall any bridge problems.
Here's a few sample pics I took for a visual aid....

This is a shot (the only one I could find) of not really our campsite but a pic from our site looking out to the bay.

I dont recall where this was taken, but we were exploring the island and there was a road side trail we walked and after about 1/2 mile it brought us out to this opening and then onto a boulder beach on the ocean.

Lighthouse...a must see!

Pic from the carriage trail.

Pic from the carriage trail (sorry my bike got in the way).

Pic from the carriage trail.

Pic from either Northeast Bay or Bar Harbor.