There is plenty of excellent fishing in Aberdeenshire. It really depends what type of fishing you're after. It just seems a bit mad if your flying to Aberdeen, to have to drive 4 hours to get fishing???!!! (Go to Caithness, or where-ever....no need!!)
Take a look at
www.fishingthefly.co.uk There's a good number of decent small stillwaters on there. Loch Insch is particular is excellent, although the likes of Haddo, and Artloch, Pitfour and Delgatie amongst others, are definitely worth a day each too. Theres an abundance of fly life up there, and the evening rises are always something to behold. All well stocked with ver good quality rainbows and browns.
However if decent sized wild browns in running water is your thing, DO NOT miss out on a day on the River Don, one of the best Brown trout rivers in Europe. Aim for beats such as Monymusk, Forbes Arms, Castle Forbes, (mid river) or move further up to Kildrummy or Glenkindie.
Don't forget the Deveron, especially roundabout Huntly. There's some cracking brown trout water which has been overlooked for years as it was mainly treated as a Salmon/Seatrout river.
Have a search in some of the magazines for articles in particular by Paul Proctor who has been up there a fair bit in the last three years....amazing stuff.
I don't know what the situation is on the Ythan Estuary these days in September. The tidal fishing for seatrout used to be monumental, although it went off the boil for a few years, but now seems to be improving again. A slime line with a nice brown or white sand-eel immitation is all you'll need there
Once you have an idea about where you're fishing, it will be easy to sort out accommodation. Theres plenty b & b's all over the place, but depending on your budget there are some cracking hotels.