Hi Daithi
Assume you'll be getting the ferry into Ardrossan?
If so, first stop should be to Culzean Castle in Ayrshire. Fabulous spot.
In general, I'd say head up the west coast into the Highlands. From Ayrshire it's motorway all the way to the north-western outskirts of Glasgow, then good roads along Loch Lomond side. Beautiful drive, plenty parking places. When you get to Ardlui - about 45mins from Glasgow, you can turn left onto the Campbelltown/Tarbet road, maybe stop in Inverary which is a lovely town. Great scenery all the way down that road.
Alternatively (or you can do both) stay on the A82 at Ardlui & head towards Crianlarich.
From there, onwards to Rannoch Moor & you can either turn off towards Oban - a nice town in itself & the base for ferries to most of the small islands. Or on through stunning Glencoe to Fort William. Plenty there to keep the kids amused, plenty decent accommodation. Maybe base yourself there a few days. (If you go to Oban, there's another road from there to Fort W - less than 1 hour).
From Fort W, you can head towards Mallaig, passing Glenfinnan where a lot of the Harry Potter movies are filmed - the kids will recognise the viaduct! Beautiful beaches further up this road (as seen in the movie Local Hero?)
Heading north from Fort William, maybe head for Skye- absolutely beautiful. (before you leave, go up the ski-gondola just north of the town -open all year, stunning views!)
Or head further north towards Ullapool.
Most towns of any size at all will have stuff to amuse the kids, and in particular plenty of outdoor pursuits.
When you've parked the car for the night, a pint will cost you around 3 euros.
OK, this has turned into an advertisement for the Scottish Tourist Board! so let me know if you want help with anything in particular, & I'll do me best for you.