The lochcharron interactive clan map here suggests that modern aberdeenshire was split between a number of clans back in the day.

Leslie, Gordon, Forbes, Hay, Fraser, and Keith all held land in the area. If the OP could narrow things down to a city or town, that might give a better idea as to what clan his ancestors may have been affiliated with.

If that information is not available, I would probably go with one of the previously mentioned options if they meant something to you (Aberdeenshire for example).