Daily demands to go to the store and will not give up until you take him. Any suggestions?

I want to make sure I'm understanding clearly, is mom driving and taking him or are you and your sister doing all the transport? It sounds like maybe mom shouldn't be driving anymore either but if that's an ongoing process maybe this could be used to give her a reason to either stop or at least cut back. My thought is you could look into senior van service/transport in your area for them and then dad can arrange rides if he really needs to go to Walmart that badly more often than you and your sister can provide. This way you could set up a regular system as an example, every Saturday either you or your sister will take mom and dad shopping for the week, if they need to go again before the next Saturday they can make arrangements with the van. In my mom's area the public bus service offers door to door van rides anywhere in town for people unable to use the bus and this is what I'm thinking about. The other option is Lyft or Uber and if they operate in your area there is a service like that particularly for seniors that allows family to provide rides for others and bank the time for their LO to use in lieu of money. It's a great idea and service just not in as many areas yet as would be helpful. Anyway maybe something like this that puts it in his lap but makes him have to work for it a bit will either get him actually taking care of himself or at least make it easier on everyone without denying him.

Sounds like he just wants to get out of the house. My step father and his wife are addicted to shopping at Costco and Sams Club, when he was driving they would go several times a week, we cleaned out their house, 60 boxes of plastic bags, 40 rolls of aluminum foil, unopened, 20 boxes of Q-Tips, the 300 qty, unopened,16 bags of the giant economy bags of spaghetti, more, and, more...you get my drift. They would buy just to buy, it gave them something to do, and it was such a deal! Now they have to take the shuttle so they only go once a week, we are moving them here, I can hardly wait to see how much crap they have accumulated in 4 months. I would buy a supply for the week, tell him that is it. And no advance on his allowance, he definitely has reverted back to being a child. Also,I think that he might be panicking as Walmart might run out, hence the behavior. Is he on any meds for depression or panic disorder? Your mother needs to walk out of the room when he starts with the demands, say no and walk away, he will give up eventually. Right now he knows if he keeps up with tantrum one of you will fold, he is a child that is what children do, until he understands that No is a complete sentence,nothing will change.

Your Dad is behaving like a two year old. It could be his dementia, but would you DO this for a two year old? I think not. Time to learn to make homemade popsicles. There are kits. You can make delicious ones with the sort of smoothie recipes out there, and with REAL bananas, getting rid of a lot of sugar high without additives. Make a freezer full and take them to Mom. And hey, if they aren't good enough, what would you say to a two year old about it. "No", right? It is a bit of an obsession for him. Try to divert him with other things he may like. And look up some homemade popsicle recipes now. Wishing you good luck.