This trip got planned at the very last minute as my husband will be in London from mid to end August

This trip got planned at the very last minute as my husband will be in London from mid to end August for work. I join him in London in the last week of August and we would like to visit Scotland after he gets done with work. I have read up a lot of the Scotland discounted golf travel bags posts (as many as I could- you guys are amazing!!!). I have put together 2 itineraries (we are a bit confused discounted golf travel bags as to which one would be best for us). Would really appreciate if all you lovely people could give your opinion on whether these plans are doable and would give us a good sense of Scotland else how do we rework them.
We both are in our early 30s. Like sceneries, discounted golf travel bags castles, museums (ok thats just me) and we both are photography junkies. We are moderately fit so I guess very long distance/aggressive walks and hikes are out. Both of us would have been in London for a few days at the very least so hopefully Jetlag wont be a problem.
August is the Edinburgh Festival so you may either want more time there to soak up the atmosphere which is either love/hate discounted golf travel bags - I love it but the chaos doesn't appeal to everyone - or you may want to avoid it completely. Hotels usually fill up in August or significantly raise their prices.
Glasgow is just as close to Stirling so that could be your start/finish point. Have you found city centre car hire? More are at the airports. I've also found that its cheaper to fly from London to Scotland discounted golf travel bags than to take a train - unless you get your train tickets well in advance. Check out Easyjet - its a budget airline but better than most - you will pay extra for checked bags, admin fees, paying by credit card - but usually still cheaper than the train. If you fly by easyjet I think Luton is the easiest airport to get to. Heathrow is easiest but no budget airline option.
Flights won't really net you any extra time since you have to travel out to the airport and check in early. Whereas w/ the train - you just take the tube to Kings Cross and get on teh train. So basically city centre discounted golf travel bags to city centre are almost exactly the same.
Also on Day 1, would you suggest that we come back to Edinburgh? This would be around discounted golf travel bags Aug 26 so I think the festival will be on- thats one of the reasons why we have kept 1.5 days for Edinburgh at the end of the trip. Should we go into Glasgow instead and start the trip from there? Also, do UK car rentals allow you to pick up a car in Glasgow and drop it in Edinburgh?