I'm going assume that if this is in the middle of a shopping bonanza then there is going to be at least an hour or more before the driving is required. So no big deal.
Probably NBD, but it could vary by person. I'm a fatty and a double rum and coke would not do much to me at all. Light buzz. So, I'd still drive if it had been at least like an hour. But I know people who'd be slightly wasted after 2 shots of rum.
As long as they're not driving with a BAC of over .08, whatever.
This is where I am. Drink it, shop a little, fine.
The double is actually the weird part to me. If you had said a cocktail at lunch while shopping, I wouldn't even question. The double seems weird to me.
It depends on so many factors. For me, yes, I could do this with a good meal and some shopping time, sure. Leaving with a good buzz? No, never a good idea. Nobody should drive with a good buzz.