The midge season is from the end of May to the end of August,so go early May or Sept. onwards.Hopefully a lot of them might have perished in the sub zero temperatures that we have been getting recently.......but don't hold your breath!!
The site outside Oban is called North Ledaig & is affiliated to the Caravan Club.It is extremely well run,and the caravans are arranged in lines, not particularly attractive, but terraced so that everyone has a view over the sea to the islands.Be aware of bad weather coming in otherwise you can lose your awning!
There is also a CL at Benderloch outside Oban........see their web site
www.clsite.co.uk
The CC site at Onich is extremely popular so advance booking is essential.
Not sure what facilities you prefer but at Arisaig there is a CL with no facilities apart from water etc.( no elec ) We haven't stopped on it but have seen it.Perched above a small bay with views to die for all around.See the web site for Traigh Golf and look at the photo gallery to give you an idea........the CL is minutes from the golf course.
Mallaig isn't a very pretty place,but one can take the ferry over to Skye from there.
Hope this is of some use to you
Maureen