We spent 2 weeks in Scotland this summer and visited my ancestor's castle as well. It is on the west coast about an hour from Glasgow. Didn't go that far north of Inverness but I do have Edinburgh recs.
As stated earlier, stay close to the Royal Mile. We didn't enjoy the Royal Mile that much as it is mostly shopping, but I will say, if you see something you like buy it. We thought that we'd see the same stuff all over Scotland and were terribly incorrect. My wife spent a small fortune. I came home with a deck of cards!

We stayed at the Double Tree on Bread St and was a quick walk to Edinburgh Castle, Royal Mile, Calton Hill, and Arthur's seat. We ate at Piper's Rest in Hunter square and they had some good food and great drinks. Don't forget to drink Irn Bru. We drank one per day, easy, and we don't drink many soft drinks. We bought the "zero" version and it was great.
Probably the best part of Edinburgh was the climb up Arthur's seat. It was a bit of a hike but was well worth it to finally make it to the top.
We drove up to Sterling on Day 3 and then stayed the night in Pitlochry. Nice little town with a lot of tourist traps but some good distilleries nearby. From there we drove to Inverness and spent 2 nights there exploring Loch Ness and the area around Urqhuart Castle. Got to Hootenanny's if you have time in Inverness, especially if they have a live band. Good atmosphere and a nice little place. You'll need to book a reservation a few days in advance at least on the weekend. We ate at River House in Inverness and it was pretty good.
I can give you a run-down of the remainder of the trip if you like but I know you didn't ask for that. Let me know if you need any ideas or if you decide to stay and do other things.
Have you considered going north first and then hitting Edinburgh at the end of your trip? I ask because we wasted 3 days of car rental in Edinburgh and probably should have visited there last and saved some money o on the rental.
We had a great time and really needed to spend about 5 more days there. We would love to go back some time to "finish" our trip. I would love to go further north the next time. Have fun!
Double Talkin' Jive...