We fly out of Edinburgh on April 25 and so I want to be back in Edinburgh the day before at the latest. We will be leaving the Aviemore area on April 23rd probably between 8-9 AM. On our way back towards Edinburgh we will be stopping at Dunnottar and probably another castle probably Scone Palace(or if there are better recommendations for 10 & 7 year old kids I'd appreciate it). Is it worth staying in Perth the night of the 23rd after Scone or should I just head back to Edinburgh that night and drop the car back at the rental agency (do agencies in Edinburgh do after hour drops?) and that way I won't need to deal with driving in the Edinburgh area during a week day and will have another full day in Edinburgh on the 24th to give us 3 full days there total during our trip.

Thanks for any advice

Do the kids like ruined or 'lived in' castles best? If ruined, have you thlough about coming back by St Andrews which has a wonderful ruined castle, with bottle dungeon, mine and countermine...
St Andrews Castle, Fife | Historic Scotland Guide

Aviemore to Dunnottar to Perth is a pretty convoluted route. where will you have been before aviemore?

i would NOT drop the car in central Edinburgh. It is much easier to drop it at EDI, whether or not you stay the last night in Edinburgh. Plus you then wouldn't have to worry about the opening hours.

I am assuming they are going to enjoy ruined castles more, but they would also enjoy "lived in" castles that had some fun grounds with mazes or such.

Our Itinerary is looking to be:
April 14th: Land late afternoon stay in Edinburgh not counting on any sight seeing this day....(Staying at Waldorf Caledonian)
April 15th: Explore Edinburgh
April 16th: Explore Edinburgh
April 17th: Pick up rental car and head to Stirling Castle, Glencoe and spend night in glencoe/fort william area.(still debating where to stay over)
April 18th: Drive to Isle of Skye and explore..Stay in Bosville Hotel in Portree
April 19st: Explore Skye Staying in Bosville Hotel
April 20th: Explore Skye Staying in Bosville Hotel (though debating about changing this one to a place back around the bridge area or just past such as Kintail Lodge)
April 21st: Drive from Skye and Stay in Aviemore area .....stay in Hilton Hotel Colyumbridge 2 nights
April 22nd: Stay in Aviemore again
April 23rd: Drive to Dunnottar Castle, and another castle if enough time and stay over somewhere on path back to Edinburgh or just head back to Edinburgh
April 24th:Return Car stay in Edinburgh
April 25th: Fly home.

>>April 17th: Pick up rental car and head to Stirling Castle, Glencoe and spend night in glencoe/fort william area.(still debating where to stay over)<<

Stay in Glencoe -- if you can get a room (it is very popular) stay at the Clachaig Inn https://www.clachaig.com/

>>April 23rd: Drive to Dunnottar Castle, and another castle if enough time and stay over somewhere on path back to Edinburgh or just head back to Edinburgh
<<

Then I'd do Dunottar ( great ruin) and Glamis (a great lived in). I'd maybe stay that night in/near St Andrews. Explore St Andrews and the fishing villages the next day, drop car / stay at/near EDI the last night. (OR you could stay near Glamis the 23rd - drive to St Andrews on the 24th, and finally to EDI area in the evening of the 24th)

Thanks Janisj I knew I could count on some advice from you. I greatly appreciate it!