Only one day to choose from so many roads

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Assuming you're all coming up from the north east then A68 to get here not the A1! The you want to try and stay somewhere near the top end of Loch Lomond as there are great roads in all directions from there and you can take a few of them on the way so flip a coin and take your pick.
Taking Whitley Bay as my starting point I'd be tempted to do this.
It takes in the A68, A84, A85, A86, A817, A814, A82 which gets you Oban, Glencoe, Arrochar, Crianlarich, Tyndrum, Loch Earn, Loch Tay, Loch Lomond (not necessarily in that order) all of which are great roads with plenty of biker friendly places.