Do bear in mind we don't use a caravan or camp so while I know a good few launch sites in the West Coast area some of the other lads that camp/caravan/motorhome will have better knowledge. However here is what I could think of quickly...
If you could venture a little further north to the south of Skye Broadford has a good launch area adj the pier and puts you out into an interesting area of water. There is a very modern caravan site there called Camping Skye I noticed when doing some research recently.
Launch here...
https://goo.gl/maps/ZVtbsee8x14ULPVR9
Not too far from there is Plockton which is a lovely location with good launch facilities and again very interesting area for sibbing. Not sure about the availability of caravan pitches there though. Launch here...
https://goo.gl/maps/3wHXJ4C67EedsgBN8 My brief video a few years back taken just off Plockton… lovely area...
Just a little further south but broadly the same area is the slipway at Dornie which puts you into Loch Duich immediately opposite Eilean Donan castle. If weather is rough you have Loch Duich and Loch Alsh (with at the right tide time the exciting current at Kyle Rhea adj) to explore but then in better weather you can venture under the Skye bridge. A few mins from the slip is Ardelve campsite which might even have direct launch into the loch. Dornie slip is here...
https://goo.gl/maps/5nLK4bgZrZzhjF4d9 Again a short video setting off from the Dornie slipway...
West of Fort William there area some truly amazing sibbing locations around Arisaig and Loch Nam Uamh & Loch nan Ceall. I don't know about caravan sites though but worth asking the boys on here as there seem to be several between Arisaig and Morar in amazing locations but I'm unsure if you can launch from them.
Just south west of Fort William there is Resipole Farm Park on Loch Sunart with its own slipway. I've not been there but people speak well of it as a start location for smallcraft boating.
A favourite place of ours where we've spent four weeks over the past five years is Tayvallich on Loch Sween round from Lochgilphead. It has a caravan site, decent pub/eatery and brilliant café with shop. Most important a slipway usable at all tide states with adj pontoon... the tide range is very low here. Slipway...
https://goo.gl/maps/9ZUfs6SQit672bqz7 There is so much to explore with the boat from that location. See my holiday report from 2016...
http://www.rib.net/forum/f50/an-aero...6-a-73370.html
Hope that helps for a start.