Current reward availability is a moot point, the OP still has to get the extra 12K miles which will take a few weeks, at least.

Here's another way of looking at the arithmetic.

60K Aeroplan miles converted to gift cards = about $500 (choose a place you shop at anyway, for me that's Costco.)

Surcharge on the reward ticket from Air Canada about $700.

Total opportunity cost of Air Canada reward ticket is $1200. And you are very limited on choice of dates and will have to change planes multiple times. Travel time on the reward booking was over 12 hours in each direction.

Cost of Rouge ticket, your choice of dates, ~$1250 (it is lower if you leave July 30th so if you can swing that you'll save more money.)

That ticket is one flight, YYZ-EDI. You'll still have to add in the cost to get to GLA. But risk to the pipes is minimal. Flying time to EDI is under 7 hours but you still have to get to GLA, so I'm guessing travel time is the same whichever way you choose to purchase a ticket.

If you are forced to buy a ticket, you can be assured you are not missing out on a great opportunity, because it isn't costing you many times more what the Aeroplan option is.

Now, it will be your personal decision as to what works for you.

For some people, that extra $500 in cash to buy a ticket will make the trip unaffordable; the AE points bought you something that you'd could not have had otherwise. If that is the case, it is an excellent use of the points.

But these points also represent 2 North American reward tickets, so there may be some other trip you'd like to take with someone else.

As well, if getting the credit card forces you to spend money that you would not have spent otherwise, accumulating the extra points that way is a false economy.

Personally, I'd choose the simple routing of paying cash. Trip interruption/cancellation insurance is covered depending on your credit card. In case of IRROPS you'll be higher up on the food chain than a reward ticket. By getting to choose your dates, you get to lower the expenses in Scotland. And fewer connections leads to fewer chances for things to go wrong (lost luggage, delays, airlines going out of business.)