What a great tour to be doing! Hope the weather isn't too awful :)
I would def recommend checking out a few recumbent stone circles on your travels. Old Keig and Cothiemuir Wood are a brother/sister combo close to each other or another great set is Tomnaverie/Sunhoney/Midmar.
The Pictish stones are incredible, sadly some standing in place are now badly eroded. The Maiden Stone at Bennachie is a good one. I found this link helpful - https://www.aberdeenshire.gov.uk/leisure-sport-and-culture/archaeology/sites-to-visit/pictish-symbol-stones/