Half day ride on the way to Ballater ..

I'm setting off from my home in Northumberland on 10.6.19 ..using the A68 to Edinburgh and then onwards to Ballater ...where I will be joining friends who will already have been there for a couple of days
I'm looking to leave at around 4.30am ..and it looks like a 5hr journey without stops ..so I'm looking for a ride on the way up there which I will ride solo prior to meeting up with them later in the day ...
Any suggestions for a max 4 hour ride somewhere on the way up..north of Edinburgh ?
We are planning on doing the North Loop and Heatbreak Ridge over the next couple of days ..what would be another good ride in the area prior to me heading home on Thursday 14.6.19 ?
Thanks in advance for any suggestions ..