If you want to stay VFR (as some of us have to!), the West coast can be a 'bit difficult' with cloud building in front and on the high ground with a westerly airflow. On days like that the east coast is generally much easier.
Carlisle is a reasonable stop but on a VFR flight like this I would pick smaller and more interesting places than Prestwick. Pooleys is your friend.
If you are going to 'tour Scotland' then direct to Oban and Glenforsa leaves an awful lot out. I'd suggest going a little further north up the coast to Plockton and then either Orkney or Wick. Either means flying over some of the most rugged and desolate country in the UK (whilst it is still the UK!).
Given our prevailing weather the east is nearly always more reliable than the west for VFR flying but of course the scenery is in the middle or west!