[Closed] Aboyne to Braemar

Yes, but only as far as a mile or so west of Ballater. Then your problems begin.
Blame Queen Victoria as she ordered the stopping of the track building.
Source of the Dee is the Lairig Ghru path. Not the sort of place to take a 3 yr old.

Deeside way (old railway line) is pretty obvious on OS Maps. I know you said no roads but the best option I can think would be Aboyne to Ballater on the deeside way, then cross the river in Ballater and ride the wee B-road road (much quieter than the A93) to Balmoral, cut through the balmoral estate (access depending) to Invercauld bridge (cross on Bridge of Dee). Ride through Keiloch carpark, Invercauld house and continue on track along North side of Dee (turns into an unclassified road at Quoich) all the way too Chest of Dee. I wouldn't want to go any further than that with a 3YO as as daveatextremists says it's a rock strewn single track path.

The worst bit would be the 8 miles from ballater to balmoral on the road, but it's a pretty quiet stretch. I'm assuming you're talking about trailer or seat?

^^^^ Dave makes an excellent point.

I was going to post the Deesideway trail route map but noticed the 3 y.o. Bit. Optimistic I'd say.

If you fancy leaving the 3 y.o. at home though, have a look at this:

https://deesidetrail.co.uk/route/

The source isn't actually on the Lairig Guru i.e. it's not the Pools of Dee as they don't actually feed into the river. The source is the Wells of Dee on the Braeriach plateau.

The bridge at Linn of Quoich no longer spans the river and Liz is now in residence, ruling out Balmoral.

^^ Fair point. Braeriach even less suitable for a 3 year old. Social workers might fly in by helicopter to take charge..

Liz is now in residence, ruling out Balmoral.

Well, I'm sure the resulting, er, escort would help with the 3 yo 'problem'...

I was going to point out where the Dee starts! Even the quiet side of the road isn't really.