Congratulations on your pregnancy OP. Will this be your first baby? I would have thought the same as you before i had children, but now I have 3; a 4yr old, a 2.5 year old and a 6 month old, and sometimes we need to go to the supermarket together. So with the two smaller ones in the trolley seats, and 4 year old walking i can manage, but sometimes, on bad days, when everyone is tired from no sleep and 5 am starts, and bickering all day, and the 4 year old keeps running away and touching things, then yes, i do let him stand in the trolley.
When i was heavily pregnant with DC3 the two lads were of an age to be fighting, climbing, running; it was like they both had the terrible twos at the same time. I tried them in the trolley seats side by side but they fought, physically, and tried to climb out or stand up. it was unbearable. So then i tried to let them walk, and they ran away. Running after two naughty boys when you are 8 months pregnant, and exhausted from minding them, being up at night, very early mornings, and no naps ever brought me close to tears, as did the judgy looks of other shoppers as i tried to control my two very spirited boys, picking them up physically, poor bump.
So then I put one in the trolley seat and the other standing at the front of the trolley, and we got on ok, until someone meanly told me off for doing it, and so i cried hormonally, left all my shopping and took my boys home.
So maybe would it be ok in some circumstances to allow a child to stand in the trolley? Or could supermarkets design some new trolleys with a front and back seat, or a buggy board or something, please?