There's a nice site at the end of lake Bled that's worth staying on. It's a bit crowded around the entrance where there are marked pitches, but as you move further through the site there's more room and trees for shade.
There's a nice restaurant at the entrance and the reception staff speak good English. There's also a nice little beach across the road, we really enjoyed our stay there en route to Croatia from Austria and wished we'd not left Slovenia upon our arrival.