Perspective itinerary?

Your drive times are all optimistic even if you don't stop by about 25% plus you will want to stop and takes photos en route.

I would stay in Glencoe rather than Oban as the main reason for picking Oban would be as a base for the ferries to the islands, which you aren't covering. Personally, I wouldn't bother with Loch Ness - there are many prettier lochs in the area.

At that time of year, you may still get plenty snow, so be prepared.

Thank you so much for your feedback... We ran all or our drives through via Michelin and Google maps and chose the longest of all routes as a worst case scenario... Why would you add 25%, just curious?

Also, I want to add that husband is very experienced in driving in Ireland (which is the same they have in Scotland).

Your times are optimistic because the estimates assume maintaining a speed of approximately 60 miles per hour. This estimate does not figure in road work (which we encountered quite a bit of when were were there a couple years ago) and the fact that driving consistently at 60 miles an hour in that part of the country just doesn't happen! Given the time of year you are going, you will encounter (at some point at least) rain and perhaps even snow - so, adding another 25% to travel time will give you a better approximation of the time involved.
Having said that, the trip you've laid out isn't rushed so adding an additional hour plus to your travel times won't impact your trip substantially.
I would agree with the other poster that I would probably opt to stay in the Glencoe area versus Oban since the main draw of Oban is as a jumping off point for the Highlands and Mull/Staffa/Iona.

I agree that you are optimistic with your driving times, but your itinerary, in general, is good. I too would opt for Glencoe over Oban. Or, just go to Mull. Check to see if one of the other ferries off Mull is operating and you would have a great drive to Skye via Ardnamurchan.

Here are a few suggestions. You'll be renting a car for the entire trip, yes?

Instead of staying in Inverness itself, consider Nairn, which is just east of Cawdor Castle. It's convenient to Culloden Battlefield and Clava Cairns as well as Cawdor, and has a scenic beach and marina. I can recommend Tali Ayer bed & bkfst (but there are dozens to choose from) and The Classroom restaurant.

On the shore of Loch Ness we found both Urquhart Castle and the Loch Ness Centre & Exhibition to be well worth visiting.

I'm not sure why you are going to Stirling before Edinburgh; I might do it the other way around. But you might be scheduling it according to which days of the week are better for getting a golf tee time or which points of interest in Edinburgh are open on which days. It's not a big deal, I just tend to aim for the further point and work my way back when planning an itinerary.

Glencoe would make sense; Oban not so much. Again, I would head for the Isle of Skye first and work my way back via Glencoe.

Make sure to give yourself plenty of time to drive back to Inverness and turn in your car. Road closures can happen, and as others have advised you may encounter snow and ice.

Have you booked lodging for the itinerary you noted? If not, consider a counter-clockwise journey, starting at Inverness, perhaps go west to Kyle of Lochalsh, and take the bridge to the Isle of Skye. If you're going to Skye from Glen Coe/Oban, you'll have to take the ferry at Mallaig or drive out of your way to take the bridge. Regarding the Isle of Skye, we visited Skye in early May of this year and it rained for all three days we were there, and for two of the three days almost gale force winds. We were prepared for the poor weather, but March, yikes. I may be wrong, but if you're expecting to witness the ethereal landsacpes that always accompany a description of the Isle of Skye, I hope you're not disappointed.

Back to the itinerary, as you have a car and if you arrive at Skye via the bridge, depart Skye at Armadale (the south end of the Isle) take the ferry to Mallaig and on to Ft. William. I'd suggest lodging in Ft. William rather than Oban or Glencoe Village as there are more lodging places (I don't know about availability in March though), then drive to Glen Coe and on to Oban. Oban is pleasant (in May at least), but I'm not certain I'd make a stop there unless you're taking a ferry to the islands. Then head to Stirling and on to Edinburgh. Having a car in Edinburgh will (arguably) be more trouble than its worth, although if you drop it off there (and take the train to Inverness--which is a very nice journey) then you'd have the added cost of drop-off at a different location than your pick-up point. As an aside, we took a half-day "tour" from Inverness including a boat on Loch Ness to Urquart Castle and back to Inverness. I elected to sit outside at the stern on the boat trip, it was a blue-sky kinda day but I was just just about frozen when we arrived at the castle (I'm just thinking of March).

I know Glasgow isn't on your itinerary, but this is just a thought. If you drive from Glen Coe to Glasgow, and spend the 2 nights you are planning for Oban in Glasgow instead, you could leave you car in Glasgow when you arrive, take the train to Stirling as a day trip, and have 2-3 nights in Glasgow, or split that time between Glagow and Edinburgh. While in Glasgow, we used the train and visited Stirling Castle, the Bannockburn venue, the Falkirk Wheel and the Kelpies as a day trip. We started early, around 8:00, and arrived back in Glasgow around 20:00, but it wasn't "rushed". From Glasgow take the train to Edinburgh, and the train back to Inverness. This way, you'd save 7 days car rental, perhaps more than paying for the up-charge for the drop off in Glasgow.