Cruachan Farm site on the North Bank of Loch Tay is O.K, more towards the West (Killin) end of the Loch which is know for it's pike but only about 15 mins drive from the east end which is reputed to be fairly good for trout. Not really on your way though.
There are a couple of campsites where I have just been in Assynt, one at Achmelvich and another at Clachtoll which have decent fishing within about 15 minutes of each one. If you are heading that direction wit a tent, take plently of insect repellent!!
Cheers
Ben