Shopping Carts

Road Runner Folding Grocery Cart by Trendy Carts

We're giving some thought to a grocery cart and I noticed on Amazon that there are a few variations on a theme.  I don't see the kids giving up milk just yet and we always need food.  With a large cart, we can take the Number 22 city bus down to Meier's and stock up when the weather turns really hot or really cold, or wet, or snow.....we have a bus stop near our house and it goes directly to a grocery store without needing a transfer. 

Do kneeling buses kneel for shopping carts?  Does 2 or 4 wheels work better? Any advice?

Astrid