Hi Wilde1, just catching up with this thread having been away. You've chosen a good route but my suggestion would be to leave the Lakes until another time so you have more time to see Scotland. I fear that you'll end up doing too much driving and will regret not being able to stop at places you pass through.
Scotland's a big place and you'll find that the roads up the north west are much slower than in England. Taking a different perspective, turn the map upside down. You're effectively going to drive from York to Plymouth (Cairngorms) in one go, then on to Land's End (Ullapool), Skye etc spending just one night in each place, finishing around Bristol/Gloucester (Ft William). We spent a fortnight touring Cornwall alone so it seems a stretch to try to fit all of this into just 5 days - there's so much to see !!
So given a couple of days 'freed up' by not going to the Lakes, why not spend an extra night near Aviemore (I'd recommend Rothiemurcus Campsite) and another either near Arisaig (suggest Camusdarach) or Glencoe ?
You'll find my recommendations for campsites (and a lot more) on my
blog. You might also be interested in my review of
Applecross Campsite as well as a post on the
most scenic journeys as part of my 'best of Scotland' recommendations.
PS The little snow we've had this winter has all but melted from the mountains - none of the ski resorts are open at the moment and this is supposed to be peak season. Unless there's cold weather coming over the next few weeks I wouldn't worry at all about snow.