Sounds a bit like what Dad wants to do, see everything. But Dad should realise that 3-year-olds have no inhibition about showing their disapproval, and will disapprove of a longish drive every day, even if they don't immediately show it. Dad should also realise that trying to see everything he'll probably end up seeing very little. I'd choose a smaller area, or perhaps two, and do some shorter-distance exploring of that area. It doesn't need a famous name, in fact it is less famous places that are often the more enchanting. More opportunity for the kids to have fun, on beaches, in streams, over rocks. Torridon would be a good centre for a few days. Morvern and Ardnamurchan, the area just over Loch Linnhe via the Corran Ferry from near Glencoe, could easily fill a week.