H.M.
maybe this well work I did it with my 4 kids it took a few times but now they behave when we shop I well ask them all to
be good before we even get to the store,then while parking i would tell them the things we need to get and have them each pick something they well look for on our list,then I would tell them if they do a good job they can get 1 thing very small/cheap{mind you there were times we were in the middle of shopping and they all started acting up ,so I would just tell them lets go and we would leave the store and no one got anything intell I could go by myself to the store}you can reward untell you feel they do not need it any more, my kids go shopping with me now and most of the time we only get the things on the list with no acting up but it did take a few trys brfore we got to this point.........hope this helps