If you want a nice lazy paddle down a beautiful river, try the West Branch Susquehanna near Lock Haven, PA. We started at the "black bridge" as us locals call it, which is a train bridge over the river near village of Farrandsville and exited at the boat launch in Lock Haven. There are rest rooms with picnic tables at the boat launch and if you never been to Lock Haven, it's a nice quite town.
The run is 4 miles and if you take your time it will only take about 1.5 hours and only once did we scrape bottom which is at the first turn just below the entry point. We went during the week and only encountered one boat on the way down.
If you want a longer run, try going from Hyner down to Lock Haven which is a 21 mile run. The river has a slow current and normally has an upstream wind, so we typically paddle the entire way. There are very limited class I rapids, this is a pretty calm kayaking trip. Great scenery, I love paddling this river. It can be busy on the weekends near Lock Haven, but boats typically can not get past that low spot near the black bridge, so from Hyner down to there is pretty isolated kayaking.
There are no accommodations or facilities at the black bridge, but Lock Haven has a couple of motels (we stay at the Best Western) and lots of places to eat. There are bathrooms at the exit point in Lock Haven, which is 300 yards on the left side of the river past the Jay Street Bridge which is the first bridge you will encounter coming down the river. Exit point is on opposite side of river of Lock Haven.
Just to go Lock Haven, PA and go across the Jay Street bridge in Lock Haven and go left immediately after bridge, the drive 4 miles along the river to the bridge. There is only one railroad bridge on this road and it is nearly 4 miles once you cross Jay Street bridge in Lock Haven. Park under the bridge and there is a small trail down to the river. Locals swim here on the weekends, so parking can be tight sometimes.