Ria, the way I read it the answer is yes, you can go, however, this is what the ex and I have worked out should we have to shop for each other. So, for you and Nadine:
Nadine gets the veg and takes it home. You go round and toot your horn / phone or text. Nadine opens the door and puts the veg on the step then goes back in and shuts the door. You get out of your car, go pick up the veg and drive away. It would also work if Nadine brings the veg to you and leaves it on the step, toots, you pick up.