We have our itinerary and accommodations all set for our trip to Scotland but need advice on how we should travel.
1 - Our first 2 nights are at the Holiday Inn City (not our first choice but rooms elsewhere were filling fast) Is this within walking distance from where the airport bus drops you off in the city center?
2 - we had planned to take the train up to Aberdeen, mostly for the experience. Then we were going to rent a car for the rest of our trip. It seems the car rentals are at the airport, so we would have to hire a taxi from the train station to the airport. Is that correct?
3 - would it be easier/more economical to rent a car right from the airport in Edinburgh when we land, although we don't think we'll need it while we are in Edinburgh. Or, should we take the airport bus back to the airport when we are ready to go to Aberdeen and rent a car then?
4 - Our last 2 nights are back in Edinburgh, staying at Ardenlee House. We'll be arriving from Dumfries area. Should we keep the car until we leave for the airport or return it and take a taxi to Ardenlee House and spend our last 2 days walking around Edinburgh?
Any advice is more than welcome. We are 4 women who have never been to Scotland, never driven on the "wrong side of the road" but are up for the challenge.

Given you are spending a couple nights in Edinburgh first it's far cheaper to wait until you leave to hire the car - the cost of car parking alone would be far higher than the bus fare. Don't hire from the place next to the HI as it has a bit of a bad reputation.

Don't know your plans from Aberdeen so can't comment on whether it's better to hire at Aberdeen - and a quick google shows several major car hire companies in the centre of Aberdeen so I don't understand the comment about "the car rentals are at the airport"

I actually didn't look at the car rentals in Aberdeen, our group member who booked our b&b in Aberdeen said the only car rental was at the airport. I will check that out, thank you. From Aberdeen, we are traveling to the Inverness area for a few days and then down towards Dumfries before heading back to Edinburgh.

I believe we've decided to rent a car at the airport in Edinburgh and drive to Aberdeen. Any suggested routes? I did a mapquest but I know sometimes those aren't the best routes.

The route you take will depend on how much time you have. The most scenic route to Aberdeen would be along the coast and through the East Neuk villages. I'm not good at remembering specific road numbers, but a good map should give you all the information you need.

After the Forth Bridge follow signs for Kirkcaldy, then head east along the coast on A (?) road and up to Elie, Pittenweem, Anstruther and Crail ( picturesque fishing villages) and then on to St. Andrews which makes for a good stop also. If you're running short of time, just head for the A 90 (I believe) to Stonehaven, be sure to allow time to visit Dunnottar Castle.

Dunfermline Abbey and its ruined Palace are worth a stop (after you cross the Forth) if you have the time, but it can be a bit of a hassle driving through the town.

I'm not all that familar with mapquest as I prefer AAroadwatch.co.uk, but with both you'll neeed to allow for more time than they indicate.