Lots of great places along that route. Living in Aberdeen & originally from Peterhead I’d personally miss out a few of the stops along the way. Stonehaven Is definitely worth a stop for the old harbour & great fish & chips fro the bay fish & chip shop. Aberdeen’s got a nice botanical garden at Duthie park, nice beach front & the maritime museum is worth a look if you want to know a little about Aberdeen’s fishing past & the offshore industry. Peterhead is a quiet town, not much happening but has a nice bay & the old prison tour is supposed to be very good although I’ve yet to do it. The drive from Peterhead to Fraserburgh is uninspiring but once past Fraserburgh the coast really opens up & here you’ll find some real gems. From Pennan to Crovie (definitely worth a visit) near gardenstown & on to Portsoy, Cullen & portnockie you can’t go wrong for scenery alone. As said Lossiemouth has a cracking beach. From here the options are endless if heading into the cairngorm national park but aviemore & Loch Morlich are must do’s I’d say, braemar, balater, Loch muick.... hard to say what the best route would be. If you like your whisky you’re spoilt for choice for distilleries & tours. The drive back from balater to Banchory is a nice one north or south side of the river. Worth a drive over the cairn o mount too from Banchory via the bridge of dye to fettercairn. I could go on but you get the idea...