Just thought I'd revisit this, one year and a bit on... in case anyone is curious in the future...

DD is now 2yrs 9mths (3 in Feb) and DS is 16mths. I can now take both kidlets shopping with minimal stress and frustration and most importantly, minimal tantrums.

We get a trolley with two seats and at the start of the trip DD is generally walking and DS in the seat. DD knows the rule for shopping - stay where mummy can see her or she goes in the trolley (or pram if we aren't at the supermarket). She'll walk happily with me to the dairy aisle where we grab a couple of Calciyums, she goes in the trolley seat next to DS and they have their milk. Once she's done, she can hop out if she likes but generally my aim is to get everything while they are having their milk. And then get out of there

If we aren't going to the supermarket, even at the general shops she is pretty good... if she behaves I give her some kind of treat so that helps, a lot.

Now to work the same magic on DS...